Yes, it's definitely getting worse with Music.app from release to release. I had success with deleting the artwork database and letting it rebuild itself, but I don't know if I just got lucky.
! Use at your own risk and only if you have a backup !
— it's only tested on my Mac so far, not official advice, and highly experimental.
OK, if you've read the disclaimer above you could try on Terminal.app with Music.app closed
rm ~/Library/Containers/com.apple.AMPArtworkAgent/Data/Documents/artworkd.*
rm ~/Library/Containers/com.apple.AMPArtworkAgent/Data/Documents/artwork/*
Now close AMPArtworkAgent via Activity Monitor.app and restart Music.app.
It should then slowly rebuild the album covers.