The controls certainly took some getting used to, but once I got the hang of it, everything worked pretty well. In that sense, if anything, I'd say this game had too many buttons. The turrets role as enemies was pretty underwhelming for me. I don't think I ever hit a turret for the purpose of stunning it, although i would sometimes jump to them earlier than I had to, to negate the possibility their random shot would snipe me on the way in.
Really nice level design. Good difficulty scaling, if a bit on the harsh side. Ended in a good place.
For things I might change, first, if I could get away without having to use the mouse for the slash attack, sort of similar to Celeste's four direction dashing, I would consider using that with a larger aoe on the attack to simplify the controls, although the existing controls do work once you get a hang of them. I managed to catch on eventually, but I imagine some people would have a really rough time of it.
Secondly, this game has a lot of red going on, although you made good use of changing the values so it still reads very well. I'd look into taking the red out of the background and floor options red floortiles and reserve it for enemies their attacks, and the wall hazards. While everything worked, the green wall hazards especially didn't read that great at the edge of my vision depending on the wall color. It was a nice way to break up the monotony to have multiple wall colors to work with though.
It would also be nice if the camera moved ahead of you a bit based on your recent movement trend, especially when you are moving downward. With less visible screen, and the tendency to bounce up when you slashed something, the downward sections seemed a bit unplayable.
As a bonus, just a touch of movement in the clouds, whether in the parallax style, a slow pan, or both, would have been nice. In general though, the clouds were a great look for the background.