>>864784864 year teammate here, no fooling here are some actually things she has mentioned or affected her over the years:
-Perms are aids. Have to schedule specific days weeks in advance just to play a game. If you want to play multiple games on one stream you have to ask each company if they're okay with that, specifically. Can't play with mods unless the mod creator gives you specific permission. Not just regular permissions, but hololive-specific legal procedures. Insane hastle
-Increased restrictions on creative projects. Holo started blocking her from using her commissioned 3D projects in the middle of her career, which is why a lot of them like amebee disappeared. They let this one up starting earlier this year but it can still be a hastle getting Cover to allow you to use something considered off-model
-Insane management issues. Meetings are all on japanese time so they constantly are up in the middle of the night because Cover refuses to work on the talent's schedules. This is why Ame's announcement was at 2:30 AM EST, so Cover could make the actual announcement at 4:00 PM JST. Most of the meetings are useless and could/should be emails or ignored.
TLDR; Ame likes to stream whatever whenever and the increasingly business-oriented cover conflicted with this, so she decided to back off.
Personally I also think she struggled with spending months at a time in Japan grinding away rather than streaming, but that one is conjecture.