I agree with the OP. The first priority should be to get good at tactics as without a strong tactical base you just aren't going to get very far. You can still study other things, and playing/analysing/looking over master games is another essential area, but predominant study of the opening is pretty much a waste of time. This is especially so if you approach the opening in a 'cramming lines' approach as opposed to plans and idea.
Opening Theory Is Pointless For Most People That Will Ever Play. Why Bother?

Opening theory isn't about memorizing all of the moves per se, since there are so many variations. The point of studying opening theory is to learn the positional and tactical themes of each opening, either so you know how to (or how not to) play with or against certain openings. You can't just put all of your faith in tactics and expect to know what to do against any given position, because those positions are determined by the opening.
On the other hand, it's important to study tactics so that you know what to do in any given position when it arises.
So the point is, study both.


I think the point that a lot of people are missing is that the average player only has a very finite amount of time to study and improve his game. Sure, technically, if you had unlimited time, it would be better to invest some in learning openings in depth and studying opening books, for example. But the truth is that the average 1500 level player will gain only a very little bit from each hour of opening study, much less than with each hour of studying tactics for example. So yes, in this regard, studying the opening is indeed pointless (unless you know absolutely nothing at all, not even the basics)

Knowing at least 13 moves in for most openings (my goal) at least helps you understand how to get to a middle game where you can use your tactics and an endgame where you have a shot. Knowing at least eight moves in on unusual openings at least helps you not make major mistakes and fall for traps those openings tend to use . . .
... I only say that for an ambitious chessplayer opening must be the least of his concerns and only after other VERY important skills have been developed. ...
"... This book is the first volume in a series of manuals designed for players who are building the foundations of their chess knowledge. The reader will receive the necessary basic knowledge in six areas of the game - tactcs, positional play, strategy, the calculation of variations, the opening and the endgame. ... To make the book entertaining and varied, I have mixed up these different areas, ..." - GM Artur Yusupov
"It is important for club players to build up a suitable opening repertoire." - GM Artur Yusupov (2010)
... Let me tell you one.My teacher got the IM title without ever studying openings.He read his first opening book when he was already IM.From those that were in the same class , the opening geniuses that always won him when they were kids didn't manage to to be even CMs. ...
"... you do need to study openings at every level. But until you reach a very advanced level, what you need to do is master the principles, ideas, pawn structures, strategies, and tactics of the openings you play, and NOT to memorize long opening lines." - FM chuddog (April 24, 2017)
... Those with good and not superficial understanding of the middlegame and the endgame will always find ways to avoid opening preparation and still play a wonderful game. ...
What about those with middlegame understanding that is somewhere between "superficial" and "good" (as classified by DeirdreSkye)?
... There are many examples.Larsen went all the way up to No 4 in the world with mainly off beat lines that had no theory(he was the first one that played regularly 1.b3 which become known as Nimzowitch Larsen attack). ...
"Bent Larsen ... MOST PLAYED OPENINGS With the White pieces: King's Indian ... Sicilian ... English ... Uncommon Opening ... With the Black pieces: Sicilian ... Queen's Pawn Game ... Caro-Kann ... Reti System ... English ..." - chessgames.com
http://www.chessgames.com/player/bent_larsen.html
... Pavel Blatny's main opening against 1.e4 is Owen's defense(his highest rating 2608). ...
"Pavel Blatny ... MOST PLAYED OPENINGS With the White pieces: Sicilian ... Queen's Pawn Game ... Reti System ... French Defense ... Nimzo-Larsen Attack ... Pirc ... With the Black pieces: Ruy Lopez ... Queen's Gambit Declined ... Queen's Pawn Game ... Uncommon Opening ... English ..." - chessgames.com
http://www.chessgames.com/player/pavel_blatny.html
... Jobava has played his best games with the so called Jobava Rapport attack , an opening that has no theory at all. ...
"Baadur Jobava ... MOST PLAYED OPENINGS With the White pieces: Queen's Pawn Game ... Sicilian ... Queen's Indian ... Nimzo-Larsen Attack ... King's Indian ... Slav ... With the Black pieces: Sicilian ... King's Indian ... Caro-Kann ... Queen's Pawn Game ... Philidor's Defense ..." - chessgames.com
http://www.chessgames.com/player/baadur_jobava.html
... Studying opening when your middlegame understanding and your endgame technique is poor is good for players around 2200 and maybe 2300 but hardly the most important for the rest. ...
Who is claiming that studying openings is "most important for the rest"?

DeirdreSkye wrote:
If you play against a GM , he can win in any opening.Why is that?
Play against him any line , even one that gives you an advantage.As long as the position is playable , you will lose.
Why?
Because you can't calculate like him , you can't evaluate like him , you can't understand chess like him and although these are the most important skills of a chessplayer all you want to do is play the opening like him.If that makes sense to you, it's fine by me.
You only need the opening to get a playable position.If you need to study thousand of hours just to do that , then you do something seriously wrong and openings won't fix it.Amatuers study a lot of openings because they simply seriously lack in understanding.
Tell an amateur to play French defense.What will happen?
In a month(if not sooner) he will come complaining :
"The exchange variation is drawish" "The bishop is bad" "Black is cramped" "the position is passive".Overall he understands nothing.And then starts the wonderful journey.From French to Caro Kan , from Caro Kan to Sicilian and here comes the big laugh.Which line?
hmmmm......Dragon is refuted........Taimanov and Kan are drawish and boring.........Najdorf.........yes Najdorf..... Fischer played it , Kasparov played it.
And what about the anti-Sicilians?And he starts studying line after line after line , for hundreds of hours.Damn!Alapin is drawish , Rosolimo is boring , Closed is..........well , closed..........and all this hilarious "adventure" from a guy that can hardly calculate 5 correct moves in a row , has serious gaps in his understanding and he has hardly ever study endgames past the basic pawn and rook endings.
Will this guy be better with Najdorf.No , there is no chance he will.He will eventually hit a wall and do you know what will say when that happen?
"I need to study more openings"
I agree what you wrote; studying opening won't help you get better and most players who concentrated on opening stay low rated; why? Because you lose through blunders and miss opportunity and allowing your opponent to win, main reason is missing tactics or attacks patterns and your position deteriorate to a lost.
... Playing theoretical lines doesn't mean only that you will win from the opening , it also means you will lose from the opening.Anand lost twice in a tournament from prepared engine lines.Why? Because he doesn't know theory? ...
"Viswanathan Anand ... MOST PLAYED OPENINGS With the White pieces: Sicilian ... Ruy Lopez ... French Defense ... Caro-Kann ... With the Black pieces: Sicilian ... Ruy Lopez ... Queen's Indian ... Semi-Slav ... Caro-Kann ..." - chessgames.com
http://www.chessgames.com/player/viswanathan_anand.html

... Kramnik has turned to non theoretical lines and openings and he is No 3 in the world. ...
"... Symmetrical English ... King's Indian ... Queen's Pawn Game ... Queen's Pawn Game ... King's Indian ... Ruy Lopez ... Giuoco Piano ... Giuoco Piano ... Ruy Lopez ... Ruy Lopez ... Giuoco Piano ... Giuoco Piano ... Sicilian ... Giuoco Piano ... Queen's Pawn Game ... Exchange Caro-Kann ... Queen's Pawn Game ... Fianchetto King's Indian without c4 ... Reti Opening ... Queen's Pawn Game ... Reti Opening ... Exchange Caro-Kann ... Dutch ..." - chessgames list of 2017 games played by Vladimir Kramnik as White (skipping those identified as Blitz or Rapid)
http://www.chessgames.com/perl/chess.pl?page=113&pid=12295

Most of my wins occur from tactics, better understand in attacking and mating patterns and most the time I have better endgame technique than my opponent; noticed I did not mention opening. I was playing otb master and we off book line on fifth move and everything depended on opening principles and good judgment; In one line I needed to sacrifice the exchange to gain an advantage and it was still very unclear, I took the safe route and lost. If a player spends more time on tactics and endgame he will become a strong player. A lot time I am equal in the opening and I outplay my opponent even though we rated the same; 1900 opening expert will lose to a 1900 tactics and endgame expert because after the opening if you can't recognize the opportunities but your opponent can, you lose.
dannyhume wrote: " If a respected coach or stronger player told you should study your games for weaknesses and errors, inevitably your first weak move would be in the opening."
That's what I thought as well. Is the OP suggesting that we should ignore mistakes we make in the opening, and only analyze mistakes that seem to be tactical in nature? What about strategic mistakes? Do we leave those be as well?
The idea isn't just to identify your mistake, but to figure out why. "I didn't know the theory." That's not an answer.
That’s an excuse. Is the theory move impossible to find without prior knowledge? You played a different move because you didn’t focus on the right moves, or you thought an inferior move better than it was, or you weren’t thinking at all and made a ‘natural’ move. Once you understand this, you can then correct the mistake.
If you make mistakes in the opening, that’s great, because almost certainly the right answer is already known. You can check theory, check opening monographs, check databases and see what GMs think is a better plan. You then compare this to your thought process and figure out why you didn’t come up with it. Did another plan look more attractive? Did you just not think about it? There’s no shame in this, as it’s taken hundreds of years of GM practice to determine the best ideas in certain lines, and that evaluation still can change.
Unfortunately, mistakes in the opening can also be terrible, because the vast majority of players say, “I didn’t know the theory,” shrug their shoulders and that’s it. Maybe they memorize the book move, maybe they don’t, but they certainly aren’t improving. They aren’t getting to root cause of the mistake. A good player can find good moves in any opening, knowing the theory or no. Maybe not the best moves, but good moves.
I don’t know if I have an overall point here. Maybe I don’t. The idea, though, is theory can help you fix your opening mistakes if you use it in the right way. Just memorizing moves puts a bandaid on your mistakes, but it doesn’t address the main concern. If you don’t shift your thought process, you’re still a low-rated player inside, even if your openings are GM-theory approved for several moves.