The fact you were able to give me a ton of feedback from such a small demo is AMAZING. Being a huge Kirby fan myself, I can understand your POV.
In terms of visuals, I've definitely have heard a bit about the banding. I didnt really see the issue at first, as with outlines it felt more clear to me, but its something I'm already considering working on! Maybe not the next demo, but definitely down the road. The backgrounds do have a thin "fog" layer over them to give the game a feeling of DEPTH, as originally it all felt flat aside from the parallax scrolling. Something we might need to reconsider but I felt it fulfilled its role in making the foreground pop more.
The attacks were a tricky thing to balance. With work on stage 2 already underway and new enemy types, some things felt a little TOO good, in a bad way. Meins grounded attack used to carry momentum when starting it, which caused us to slip into the boss and take damage, leading us to remove that, making Mein stop for a more precise feeling. We did intentionally restrict Mein having multiple aerial attacks due to it making skipping large segments that much easier with a dash jump into double jump. It requires the player to think more about when they are going to use it and how to traverse the stage. It was brought up to me by others that having said restriction feels "off" and its prob worth testing again.
You bring up some valid points, which might need a second look if possible. I appreciate you trying the game out and giving me so much to work with though! Thanks again for giving it a try.