It wasn't that it was a musical, it's that the music wasn't good. The switch from reality to dream wasn't edited well in most cases.

I never had an issue with Fleck not being the Joker we expect, but if he isnt, really lean into who was. (I thought that's where we were going with the 2 fellow inmates, but no.)

So, barely(?) meeting the real Joker really breaks using Harley as a character.

That's the broken expectation. Why use the most dynamic IP of the entire franchise and never deliver?