Wow! I love the whole aesthetic and the gameplay but some of those jumping sequences are brutal! And the bosses doubly so!! I'm not sure my thumb will forgive me for all the punishment it's received from them!
I suggest to perhaps have the dash move (hold attack+run) charge one or two seconds faster than it currently does. When you first have to pull that move off into a double hookshot, it takes a fair few goes to get it right and I ended up having to walk a lot to get the run-up each time to get the dash.
I'm in two minds whether to suggest boss health bars. On the one hand, it'd be nice to know how much health the boss still has after he thrashes you for the 10th time in a row. On the other hand, they (mostly) seem to have a second phase once you get them low enough which tells you that you are doing something right.
Oh, I did find what might be a bug. There was a room with a line of purple portals and a fragment of a something. The timed objective is to hit the green arrow orbs so they line up against the wall and then use attack chaining to climb up to get the fragment.
I tried this multiple times and I could only attack chain three orbs before Ato stopped attacking and I'd fall down. I tried varying the speed/timing at which I press the attack button, but I always only climbed three orbs. After about 10 mins I gave up on that room and continued the story.
Otherwise, I found it to be very entertaining (I called it quits after the spear boss as it's time for bed!) and I hope you find success with it!