Outer Wilds.
I was actually unaware of it's reputation when I played, I just saw it on steam and thought a space exploration game sounded nice. But I just thought it was kind of mediocre. The gimmick was decent in theory but for a game about a solar system it felt so needlessly small, each location is essentially one puzzle room, and the writing of the ancients completely took me out of the game since they just talked like modern people posting on social media. It felt smaller than the original Myst with a world I didn't really care about.
Then I found out it's literally considered the best game of all time and a lot of people cry themselves asleep, lamenting that they will never be able to play the game for the first time again.