With macOS Catalina iOS sync has moved to Finder and became very unreliable, very slow, and even adding a single song starts a very long loop of syncing:
Also when you have 20-40 GB photos and videos, you are looking for something better than iCloud Photo library or Photo stream. Like a better UX of deciding what is uploaded to icloud, what is on the mac (where space is possibly limited) and what is on the iPhone, and where it's clear, that "delete" button deletes from which of the three in the end of the day.
But slowness and not showing a progress status is also a huge issue with both Music/Finder sync and Photos app.
Is there a 3rd party project out there, who got these sync tools right between iOS, macOS and icloud? I'd be happy to support them.