Opening theories not for under 1600 players?

Here is a true example of where not knowing opening theory *might* hurt someone who is a decent tactical player, has basic understanding of chess, etc.

In both cases, black just equalizes the game, and the better player will win. White played natural, logical, tactically safe moves that just turned out to not be the best ones, and notice how it doesn't leave white much worse or anything. 

paragraph 1. e3 is fine 3.a4 is best move according to stockfish. 2...a6 is a blunder by black but is played commonly by patzers and on the face of it looks reasonable just actually bad. keep in mind i stated that this is a scenario for 800-1000. these people aren't that good.

 paragraph 2: just to point out i'm aware that the queens gambit is not a gambit but people who don't revise openings don't know that. and b5 is fine in terms of principles because in the kings gambit (i know it's a different opening but my point still stands) g5 is a common move therefore b5 shouldn't be seen as not obeying principles (just bad in the long run). developing bishops before knights suggests that Bishops openings is bad, caro-kann is bad as Bf5 is used in the opening before a knight is developed. the french winawer should also not be played as that develops a bishop before a knight. modern fianchetto openings are bad because they develop bishops before knights. it's the case most of the time but not all of the time. therefore that move can be overlooked as not obeying opening principles.

tactics are more important but openings should still be revised.

Oh come on. Is this false modesty? You followed opening principles quite well. You gained a lead in development and better control of the center (regardless of how many pawn moves you made), and then launched a flank attack with a CLOSED center, correctly. When you played 10...h5, you had 5 pieces attacking white's king (Qd8 and Bc8 can be included, as they're already participating from the starting squares), and white had 2, maybe 3 defending.

Well played.

BTW, instead of 14...Bf4, black already had a kill shot at move 14: 14...Bxh2+! 15.Kxh2 Nxg4+! (better than 15...Qd6+ 16.f4) 16.Kg1 (16.fxg4 Qd6+ -+, as in the game; 16.Kg3 Qh4+ 17.Kf4 g5#) h2+ 17.Kg2 Qh4, and there is no defense against 18...Qh3#.

And in case anyone cares, it took me about 10sec to see this tactic after glancing at the game, and <1min to do all the calculations in my head. And this is why you practice tactics.

what about this. where black also follows opening principles and loses a minor piece.

^Again, black miscalculated. Such traps are pretty common and well-known anyways, but if black had better tactical skills, it wouldn't have happened. 

Also, developing pieces randomly where they can be attacked with tempo is not following general opening principles. 

The opening principles don't say to play ...Nc6 ...Nf6, etc. no matter what. 

So this is an example of violating basic positional principles as well as lack of tactical foresight.

"... In the middlegame and especially the endgame you can get a long way through relying on general principles and the calculation of variations; in the opening you can go very wrong very quickly if you don't know what ideas have worked and what haven't in the past. It has taken hundreds of years of trial and error by great minds like Alekhine and, in our day, Kasparov to reach our current knowledge of the openings. ..." - GM Neil McDonald (2001)
"... Before moving on to a discussion of specifics, here are a few general thoughts on opening play. Note that I propose a few principles rather than provide a whole list of outmoded opening dos and don'ts. I feel that such a list inhibits creativity in the opening, and encourages beginners to play like automatons, almost never deviating from the Giuoco Piano (the chess equivalent of 'Chopsticks' on the piano). ..." - FM Graham Burgess in The Mammoth Book of Chess

FM chuddog wrote (~1 day ago):

"I've been told I give good advice in these threads, so I'll chime in, illustrating with a game I just played in an open swiss this past weekend. I was black. My opponent, rated ~2000, lost in 11 moves with white. This wasn't speed chess.
Why did he lose? Is it because he didn't know the opening lines? Well, he was out of book after 5 moves. But guess what - so was I. The real problem is, he neglected opening PRINCIPLES. You don't start attacking until you've finished developing and castled. And you should never open the center when you have an uncastled king in the center. (There are exceptions, but you have to learn to follow the rules before you can spot the exceptions.)
The point is, 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.

GR vs. JC weekend swiss | Round 1 | 22 April 2017
1 e4 e5 2 Nc3 Nf6 3 f4 d5 4 fxe5 Nxe5 5 Nf3 Bc5 6 d4 Bb4 7 Bd2 Bxc3 8 bxc3 0-0 9 c4 Bg4 10 Bb4 c5 11 Bxc5 Qa5+ 0-1"

Cherub_Enjel wrote (~2 days ago):

"... The one advice that was from an FM (Chuddog) in a similar thread was one of the only ones that seemed sane to me there."