[non-classical player, who's gained interest/appreciation for classical]
I want to touch on the "classical piano" aspect of all this. I believe majority of people on this forum play classical pieces to some degree.
For me, one of the absolute hardest things to do, specific to me, is MEMORIZING anything. I can't, for the life of me, memorize any passages. that's what also makes piano "hard" for me. It's "super easy" for me to "mess around and play anything by ear" but when I do so, it's done haphazardly, and not in any disciplined manner. And it's repetitive progressions type of music.
In most (modern) genres, there's a repetitive chord progression that's unbelievably easy for someone who plays by ear. I can do that in my sleep, as can anyone who has natural ability to play by ear.
In classical, I'm always trying to remember, even the MELODY. So yes, something like Moonlight Sonata 1st Mvmt is easy, or the most basic-basic Bach stuff, or something like ionno, Canon in D (if that's even deemed classical lol).
But anything else, I'm always lost in the sauce.
I commend the many of you who have the ability (yes, it's a talent that I do not have) to memorize things.