Movements of mozart sonatas... it's so easy to butcher them!!! And I didn't understand this until a few years into university; it's so easy to hear a mistake in a lot of his music (compared to a Liszt or Rach piece); it has to be delicate, and musical, and technically perfect! If someone half-asses a mozart piece it just sounds terrible.
I played Rach2 first movement this year; the most difficult part once I had all the notes down was the start of theme 2... it's SO MUCH different playing it when there's the second part backing you up. The fast parts are more masked, but when you have the solo entry of theme 2 (which isn't difficult compared to the rest of the piece, technically speaking), it needs to speak!
I wouldn't say Le Gibet is remotely 'technically' easy... chords, cross rhythms, and keyboard facility are nightmares in this... it goes all over the place. But ya... those Bb's that repeat, they can't just sound like someone relentlessly 'hitting' those keys without intention.
Maybe the easier Chopin pieces? Some of his nocturnes and waltzes... if they are just 'played'... it could sound nice, but there are tons of expressive markings in his music, you can't just ignore it and expect to have conquered the piece.