I'm sorry ill stop at the boss, the player controller is defintely not adapted for a one-hit bullet hell boss. And the inertia that goes with that is not enjoyable for these situations.
However, the game looks formidable, and sounds neat. And there are a lot of cool levels. But the character controller feels a bit too jank. I would advise trying to make it again ! It would be a great exercise! Look back at platformers you really enjoyed, see why they worked and why is your game juuust a bit far from that!
Not sure if you have twitter but this thread by maddy thorson explains a lot of the mechanics that makes the game play good and I would recommend trying to add some ! https://twitter.com/MaddyThorson/status/1238338574220546049?lang=en