I like MY — I just wish I could design more of it on the user side.
Auto generated colorschemes are great and give Android a level of class it has been missing for a while. But I wish I didn't have to rely on a third party app like Repainter to finely choose my palette rather than hope the theme engine makes a good one. I also resent my icon shape, font, and icon options being ripped away from me.
There was a section on the original MY Google IO announcement that implies that the padding and roundness could be freely adjusted throughout the system. I wish that materialized (rimshot) into the final product.
The only objective regression I can think of with MY, rather than just an annoyance, is the Quick Settings. A merged internet toggle that no one asked for, a further reduction in a available toggles from Android 11, and not even bothering to make the Bluetooth toggle one of the fancy expanding ones instead of sending you to settings or surfacing the audio playback toggle (why can't I change the output before I play media, Google?). Ugh.