Thanks for the sympathyI understand your frustration, I have experienced similar
It would be interesting to know whether your experience was with the library on an external device and whether you have seen the AMPLibraryAgent using excessive CPU time.
One more major annoyance for me is that with iTunes I usually played my music via my Apple TV (3rd generation), so that I could output over my hifi. That doesn't work any more with Catalina, where the Apple TV (after quite a delay) reports that it cannot connect to the Library (strangely, for a short while after I installed Catalina, it did make the connection, at least when I first did a Restart on the Apple TV). The only way I can play music via the Apple TV now is using Airplay (and that has the subsidiary annoyance that on every new start of the Music app the audio output reverts to about mid loudness and I have to up it in the System Preferences/Sound/Output). I wonder too whether the problem connecting to the library is caused by some timeout related to AMPLibraryAgent's excessive CPU use (though maybe I'm just getting a bee in my bonnet about that ).