I posted this in another thread; I'm finding a (tedious) workaround to be effective.
Quit Music on all devices (actually, specifically quit it on all devices) (In my case: iMac, MBP, iPad, iPhone: all QUIT)
Shut down all devices
Start up the Mac you want to edit on; Open Music; Select File > Library > Update iCloud Library, and let it run (you'll see the updating message for a while in the bottom left corner of the window, under playlists)
Make all the edits you want to make on the Mac: ratings, create / delete / move / adjust playlists etc. etc.
When done, Select File > Library > Update iCloud Library, and let it run to completion again. You have now made your edits and (probably successfully) transferred those changes to your library on iCloud.
All of your changes should have stuck.
Now you can open Music on your iOS devices, and they should reflect the changes you've made on your Mac, BUT you will no longer be able to make any new changes stick from the macOS devices, UNTIL you re-run this tedious Quit-Shutdown-Restart workaround again.
This is working consistently for me. Hopefully the fix is not too far away. Good luck all.