Does opening preparation contribute a lot in winning games?

Question

It is often said that Opening preparation is considered one of the most vital things a chess player needs to learn when they start getting better(above 2000 elo). Many chess players are known for their good opening preparation like Garry Kasparov, Fabiano Caruana, Anish Giri, Hikaru Nakamura, MVL, etc. Most GMs prepare a lot of openings with different lines, and variations for their classical tournaments. Still, many are not able to get a win and reach the top.

I have never heard anyone say that Magnus Carlsen is very good at opening preparation. He's often regarded as a great endgame player, having good intuition.

So, my question now follows: Is opening preparation really effective and contributes a lot to win at the very top level? Or being a good endgame player, in which good intuition is better? If yes, then why do most of the players spend time in preparation? If not, then why can't they win most of their games by outplaying their opponent?

To make it more clear and easy to understand: I want to know if preparation is worth it compared to the time many titled players put into it.

Answer 1

Especially for high-rated players like titled players, YES opening preparation is crucial. Without it, you would lower your win rate by a lot.

Opening preparation is not everything though, you still need to prepare middlegame and endgame positions and theory, as well as certain positions where one can exploit weakness (mostly in openings though).

The saying "Opening preparation is considered one of the most vital things a chess player needs to learn when they start getting better(above 2000 elo)" is not wrong, as especially for me, I am stuck at 2000 blitz rating on lichess.org, as I do not do opening preparation, which of course results in my rating not increasing at all anymore.

Having good intuition is probably a combination of general theory and positions of chess and the ability to see many moves into the future, but it not necessary that opening preparation or intuition is better. In my opinion, I think both are equally good.

Most players still lose even though they have prepared a lot on openings, either because the opponent played a move that completely confused the opponent in the opening, or missed an incredibly good move for either the opponent or yourself.

If you do not plan to study much on openings (Magnus Carlsen still studied a lot more than normal people) and rather have good intuition, intuition is quite tricky to train for in the first place, so in my opinion, studying openings is slightly better.

I do not know what others think of this, but in my opinion, it is quite worth it to grind and study openings, especially after a long period of time. Doing so will lead to noticeable better play in the opening. However, if you are the type of person that does not really like long-term studying, i'd rather you study a little only, and gradually build up your knowledge over time. Obviously these GM's got their titles when theyre quite young, so they studied quite intensely on theory, especially openings, to achieve the high rating they have today.