There is literally no difference between the Muzukashii and Oni difficulties aside from the fact that all you have done to "increase" the difficulty is make certain notes that were not finishers in the Muzukashii into finishers in the Oni. The Muzukashii also features much more variation in colour changes than the Oni, which is extremely counterintuitive seeing as though colour changes are meant to become more variated as you go up the difficulties. Density-wise, there is just a 16 note difference between both difficulties, leading to there being no progression in difficulty from one diff to the next because the difference is so subtle.
Here are some screenshots showing the problems (Muzu top, Oni bottom):
https://i.imgur.com/IULFL1P.png : Why use more colour changes in the Muzukashii than Oni when it should be the other way round to make things simpler for Muzukashii-level players?
https://i.imgur.com/N8uIhfh.png : Muzukashii is harder than Oni at this point, note density is the exact same in both difficulties
https://i.imgur.com/izyBATA.png : Note density is again the same in both difficulties. Removing finishers does nothing to change difficulty and in fact X x X x X is harder to hit (if hit properly) than X X X X X, so this should be the other way round
did some adjustments