Why does my entire music library get synced to my iPhone every time

I have been an Apple user for many years now but when Apple changed from iTunes to Apple Music the syncing process between my Mac and my iPhone has been turned into a labour intensive process.

Every time I've synced my iPhone to my Mac since the change a number of years ago it has synced my entire library of music which has 21,000+ songs and it takes about 2 hours or more to complete if you add in the photos. Before the switch to Apple Music I never had this issue, it would only update the play count and changed data and such, when synced. I've searched google many times to see what I can do and have found NOTHING! I've seen many solutions about the "Work and Movement field" but none of my songs have that issue. It's not because I have iCloud Music Library enabled, I don't even subscribe to Apple Music.

I have checked the box "Manually Manage Music etc" and that also syncs the whole lot or wipes them off the iPhone.

The whole syncing process has definitely been forgotten by Apple as they want you to subscribe to Apple Music and dont get me started on that. I had a go a few years ago and lost all my play counts and meta data. Never again.

Any tips or it just doesnt work anymore ?