They say endgame study teaches the essentials a lot more directly than opening study, which can come down to just memorizing moves.
Opening Study vs Endgame Study

One opinion of opening study enthusiast, the game can be WON in less than 15 moves. Converting is ofc easier said than done.

That's true, and you're not likely to beat an experienced player relying just on your prepared openings. Even getting a material advantage in the opening doesn't guarantee a win if your strategy and tactics are weak.

End game has less pieces and posible combinations. At a certain point in end game you can already tell if a position is drawn, losing or winning with perfect play.
I don't think you can do the same with the opening because there are too many possible combinations still left and remains unsolved by computers.

I think endgame becomes more important as players get closer to the master. It's like an advanced subject that players should learn after middlegames and openings. As Magnus Carlsen has proven in many games, I think the games between the masters are mostly decided in the endgame. Endgame knowledge also tells how to proceed the middlegame.
@10
"It's like an advanced subject that players should learn after middlegames and openings."
++ No. Chess should be learned in reverse: first endgames, then middle games, then openings.
'In order to improve your game you must study the endgame before everything else;
for, whereas the endings can be studied and mastered by themselves,
the middlegame and the opening must be studied in relation to the endgame' - Capablanca

@10
"It's like an advanced subject that players should learn after middlegames and openings."
++ No. Chess should be learned in reverse: first endgames, then middle games, then openings.
'In order to improve your game you must study the endgame before everything else;
for, whereas the endings can be studied and mastered by themselves,
the middlegame and the opening must be studied in relation to the endgame' - Capablanca
That's also reasonable.
I think the process of improving chess skill is done in the order of middle game, opening, and endgame in general. Because most people experience losing by blunders made in middle games first, and after that they study openings to get into a better middle game, and they study endgame seriously when they build up enough skills not to lose in middle games.
However, I also agree that it would be ideal to study endgame first to build solid skills, because I agree masters saying middlegame is about getting into a better endgame, and opening is about getting into a better middlegame. If players can imagine a winning endgame from their middlegame, then it would be much easier to find a strategy.
But on the other hand, I think there is something vague because masters are way better than other players. Most players (including me) are not that accurate like them and cannot evaluate positions like them, so they can lose before even entering the endgame. And that's probably why people who haven't build enough skills in middle games are uncertain about studying endgame.
So I'm not trying to disagree with a method of studying endgame first(and also agree that it could be one of the best way to learn), but I usually think that what players needs to learn seriously depends on their level in a realistic point of view. (tactics for beginners, openings and positional play for intermediate, strategy for upper intermediate, endgame for experts IMO.) I think both methods are acceptable.
@12
"tactics for beginners, openings and positional play for intermediate, strategy for upper intermediate, endgame for experts"
++ No, the sequence should be
- Blunder checking
- Tactics
- Endgames
- Middle games
- Openings

@12
"tactics for beginners, openings and positional play for intermediate, strategy for upper intermediate, endgame for experts"
++ No, the sequence should be
- Blunder checking
- Tactics
- Endgames
- Middle games
- Openings
Yes, blunder checking would be the first thing. But I think for the rest there could be various opinions.

Opening study because it’s more fun. Although ideally I would prefer not to study because I am a lazy pile of garbage.

One opinion of opening study enthusiast, the game can be WON in less than 15 moves. Converting is ofc easier said than done.
I disagree. You can very easily convert it to a lost position if you're not good at tactical play.

I'm very far from being an expert, but I'm inclined to belive that the study of endgames is much more valuable than studying openings, before you became an expert ( CM at least ). It teaches you to master long maneuvers, how to use pieces to their full potential, makes you build a very deep vision of the chessboard and the collaboration between pieces and pawns, forces you to play with great precision.
For example, I'd say that learning and playing well an endgame like B+B vs K in all possible situations is already very instructive. And I think that studying an endgame like K+R+P vs K+R, even if very complex, would be instructive even at my low level ( I wanted to start studying it but I gave up, due to lack of time )
So, I think those who support the importance of studying endgames, and studying them before openings, are right.
Majority of players prefer Opening Study. Follow latest innovation in Ruy Lopez and Sicilian. Specialize in.lesd popular opening like Scandinavian and Pirc. And majority of books published are about opening. The popular endgame books remain the same.. Silmans Endgame Course and Dvorestsky Endgame Manual remain popular in the last two decades.
Which do you prefer to study if your time is limited?