Sometimes -not often, I think- I feel kind of let down by some compositions, not because I don’t like them, but rather, because they don’t live up to their promises, kind of: it could have been composed differently.
An obvious example -I think- is Tchaikovsky's piano concerto. The famous introductory melody of its first movement: it feels wrong that after that introduction we never hear it again!
A more polemic one maybe: Schubert’s also famous Andante from his second piano trio: as much as I love Schubert, and I love this trio and its andante… I wish he would have treated such an amazing melody in a different way, maybe a simple ABA structure, or even variations like Brahms's first sextet.
Do people have other examples, do you feel sometimes the same kind of thing?