Hot take: The notion that "openings don't matter" is hogwash

"... The game might be divided into three parts, i.e.:- 1. The opening. 2. The middle-game. 3. The end-game. There is one thing you must strive for, to be equally efficient in the three parts. Whether you are a strong or a weak player, you should try to be of equal strength in the three parts. ..." - from Capablanca's book, My Chess Career
"... As [First Steps: 1 e4 e5 is] a First Steps book, I’ve tried to avoid encyclopaedic coverage. In any case, you certainly don’t need to remember every single variation and all the notes before playing the opening. Take in the first few moves and the key ideas, and then try it out in your games! ..." - GM John Emms (2018)
https://www.newinchess.com/media/wysiwyg/product_pdf/7790.pdf

You don't have to believe other people about this, just do the experiment for yourself.

Start playing an opening you know little or nothing about, maybe after watching a 10 minute video on Youtube. Do it for a while. See if your rating will drop dramatically. It won't. At least not if you are the same as everybody else.

Openings really don't matter a lot. Neither do endgames. People who pretend otherwise probably have a book or a course to sell.

Chess 960 ....

@Meerkatze said in #12:

You don't have to believe other people about this, just do the experiment for yourself.
Start playing an opening you know little or nothing about, maybe after watching a 10 minute video on Youtube. ...
Not the only option. One can spend some of one's time with books like Discovering Chess Openings and First Steps: 1 e4 e5.
https://www.amazon.com/Discovering-Chess-Openings-Building-Principles/dp/1857444191?asin=1857444191&revisionId=&format=4&depth=1
https://www.newinchess.com/media/wysiwyg/product_pdf/7790.pdf
"... Review each of your games, identifying opening (and other) mistakes with the goal of not repeatedly making the same mistake. ..." - NM Dan Heisman (2007)
https://web.archive.org/web/20140627062646/https://www.chesscafe.com/text/heisman81.pdf

Beginners who are missing forks, pins, simple tactics, and hanging pieces will not improve much by studying openings but, after a certain level, knowing some openings will help them a lot, in terms of how to get the types of middlegames they want and what plans they should have, pawn structures they should be familiar with, king safety, and how to better coordinate their pieces, etc.

@RighiBilly said in #13:

Chess 960 ....

The level of complication is far too great for any Untitled player. The fact of the matter is, most of them don't even understand how far above their level the game truly is. It's bad enough when you know where the back rank is at. Scramble those pieces and the number of possibilities is simply beyond mathematical comprehension. 15 minutes for the top 20 players in the world isn't enough time for them to understand the position. Imagine what it's like for us mere mortals.

@plmw said in #15:

Beginners who are missing forks, pins, simple tactics, and hanging pieces will not improve much by studying openings but, after a certain level, knowing some openings will help them a lot, ....
Reuben Fine’s Chess The Easy Way is an example of a book that includes some consideration of specific openings as part of the effort to help beginners to improve.

@qpalzm123456 "Understanding what opening you're playing is undoubtedly important. probably #3 most important only to game review and tactic training. so why do masters say it doesn't? or is there something I'm missing...?"
Not even close. Endgames and middlegame strategy are far more important than learning openings. If you have good middlegame strategy you can generally play good moves right out of the opening without knowing any theory unless the opening is very sharp (ex: Botvinnik semislav, but I think anyone who plays that is a sadist).
Pretty much none of us know a lot of theory on the openings. Even at 2200, the level I play, at least 80% of the games are decided by blunders. At 1600 it's more like 95%. If you just blunder less and think 2-3 moves ahead, I guarantee that you can gain +300 elo.
There are players who say no to opening theory to the extreme by having a repertoire of g3 with white and g6 with black. Your take is objectively wrong since anyone can get very far without knowing a lot of openings.
Personally, I'm 2200 in classical but I play openings that result in bad evaluations by the engine in the middlegame, but I still manage to win half of these games, because I'm a firm believer that my games are decided by the better calculator

@qpalzm123456 said in #1:

... Understanding what opening you're playing is undoubtedly important. probably #3 most important only to game review and tactic training. so why do masters say it doesn't? or is there something I'm missing...?
@BabyPoltergeist said in #18:
... If you have good middlegame strategy you can generally play good moves right out of the opening without knowing any theory unless the opening is very sharp ...
How many players can realistically expect to have "middlegame strategy" that is this "good"? Perhaps, with some opening knowledge, it will be "generally" more often that some of us manage to play good moves right out of the opening?
@BabyPoltergeist said in #18:
... Pretty much none of us know a lot of theory on the openings.
Not quite the same as an "openings don't matter" attitude.
@BabyPoltergeist said in #18:
Even at 2200, the level I play, at least 80% of the games are decided by blunders. At 1600 it's more like 95%.
Is deciding a game the only issue? Isn't it somewhat important as to who is more likely to be the one to make the deciding mistake? We have notations like

=
(for "white stands slightly better"). That certainly does not mean that "white has a decisive advantage". We have a separate notation ("+-") for that. So, how can the "advantage" be anything other than it being harder for Black to avoid a decisive mistake? Isn't it therefore somewhat important as to who manages to avoid a slight (or not-so-slight) disadvantage?
@BabyPoltergeist said in #18:

If you just blunder less and think 2-3 moves ahead, I guarantee that you can gain +300 elo. ...
Before making guarantees, shouldn't we be more specific about how much "less" we are talking about? 1%? 5%? 20%? What?
Does everyone agree on what counts as a blunder?
Does it make a difference whether we are talking about thinking 2 moves ahead or 3 moves ahead?
What does it mean to think 3 moves ahead anyway? Does it mean necessarily choosing the RIGHT 3-moves-ahead positions to consider? Does it mean necessarily making reliable assessments of those positions? How reliable?
@BabyPoltergeist said in #18:
... Your take is objectively wrong since anyone can get very far without knowing a lot of openings.
Where does one find objective data on what "anyone" can do?
By the way, I saw qpalzm123456 referring to the desirability of "understanding what opening you're playing". Is it appropriate to take qpalzm123456 as writing in favor of "knowing a lot of openings"?
@BabyPoltergeist said in #18:
Personally, I'm 2200 in classical but I play openings that result in bad evaluations by the engine in the middlegame, but I still manage to win half of these games, because I'm a firm believer that my games are decided by the better calculator
So, you DO "play openings"? Anyway:
"... everyone is different, so what works for one person may likely fail with another ..." - NM Dan Heisman (2002)
https://web.archive.org/web/20140627084053/http://www.chesscafe.com/text/heisman19.pdf

The sentiment that OP is talking about is somewhat old fashioned imo. It used to be that players had less feedback from the opening and early middle game phase. We'd know if we liked a position out of the opening if it was easy or fun to play or had a clear edge of some kind (databases helped a lot to find edges). Beginners who memorized book lines, like old school eco stuff, would get to the end of memory and blunder on the very next move. So.. as a coach I did tell students that they should learn chess first and then learn the openings later.

Then came computers... If you want to know how to play a position starting at the end of a book line you can put the position into a computer. The possibility of immediate strong feedback in a previously grey area of the game has changed how chess can be learned. So now there is a possibility of learning the opening first, understanding through direct practice some middle game ideas and progressing that way.

Just.. don't forget to learn how to play chess along the way as you all study all your openings now. A solid endgame is still what makes a good chess player into an expert or master. That may never change.