Glad you appreciated my review! I love hard games. And I played Celeste a lot, have not finished it yet, but planning to.
The main goal of such a game is to provide very good control over the character.
In hard games a golden game design rule always takes place:
"If the player fails and blames the game - your design fails.
If the player fails and blames himself - you did everything right."
The game should provide good control over the character, and a decent challenge to it. I think even in the jam version you enough close to it. Good turns and removal of sliding or justification of it will help a lot.