Very fair critic, I agree with basically everything you said (I was also thinking of it as a reverse Osu! too while testing it).
The reason I went with a difficulty spike that may feel unfair, especially on a first playthrough, was that "easier" level that always give you enough reaction time to dodge might feel a bit hard at first but get really easy with prior knowledge. I probably failed to communicate that clearly enough but starting from the third level I am not expecting the player to get everything right on the first try (and playtests seemed to agree with me on that), hence why I made restarting the level as quick as possible
With all that being said, Boxed is definitely overtuned and would probably be better with a bigger area to move around in (especially on mobile devices). Sorry for that one :-)