Thank you for your feedback!
This game was made 3 years ago and I don't intend to go back to it for now, but I'll address your criticisms:
Every mon was tested throughout the entire game, so even if sometimes awkward, it's possible. That's the nature of trying to do interesting levels considering 90 different characters with different hitboxes and sizes. I had rules for how tight a space could be and that really hindered the level design process. That's one of the reasons I'm not interested in coming back to this game specifically, I'd rather make something new.
Conceptually, it was supposed to have a character select totem at the beginning of each level and a level select. Both are implemented and it's very easy do code. But it was just boring to play like that. While testing, I enjoyed it way more having a single mon for an entire stretch of stages instead of this convenient freedom of selection. Made the journey way more memorable. If you don't like it this way, it's fine. But know that it was 100% intentional.
The boxes are a nightmare themselves even for me, so I agree with you. I even started developing an update that replaced their destruction triggers from specific powers to just the mon's evolution stage. But I never made it public, which is a shame. I'll consider it if I go back to a new game.
I never thought about reverting evolution stages and then wanting to go back to the original stronger form. I added that de-evolution totem as a request from a player back then. I'll keep that in mind, it's useful to know that. I never used it playing it, just for testing purposes.
Thank you for putting your time in the game and in your thoughts about it. I really appreciate it!