When I sync my music library all playlists revert to old versions. Is there a fix?

I liked iTunes. But the update to Apple Music has been a nightmare. I do not subscribe, but I'd like to use the app to organize and play my music. I have lots of playlists and lots of music, carefully curated. All of my work is for nothing, because when I sync (using the Finder, because that's how I have to do it now), all the playlists lose years' worth of changes on my Mac AND on my iPhone. They revert to very old versions of the playlists. Basically, Apple keeps making me cry, and I'm at my wits' end.

And there's no way to turn on/off Sync Library on my iPhone (as suggested on another thread) because it's not an option since I'm not an Apple Music subscriber.

Is there any solution?

My system:

Mac OS Catalina

iMac (Retina 5K, 27-inch, 2019)

iPhone 11 Pro