Been awhile now, but thought I’d update a few thoughts. As mentioned, I had spent more than 40 hours with Apple Support trying to resolve this issue with iPhone, iPad and iMac not working together because of OS problems. It involved upgrading from Mojave to Catalina, going backwards and having to erase the iMac and restoring from TM backups, then doing the same to upgrading to Monterey, etc.etc. While the advisors and senior advisors were very cooperative in trying to help, no one could solve the problem. Basically, my music library was FUBAR because of supposed copyright issues, to which I say BS.
I eventually did install Monterey and was almost resigned to not having the library I built over a number of years on my iPhone or iPad. Then I tried something and Bazinga it worked. Simply turn off iCloud. This way Apple doesn’t tell me what I can listen to and what I can’t. I now can simply sync direct from the desktop to my devices. Still a couple of glitches in that a few songs on my iMac don’t sync over, but I can live with that.
Now I have another issue with Apple. I recently got a new iPad as my battery on the old one was pretty much used up. I purchased an iPad Air. Without checking, it uses another type of connection. This requires a USB-C connection. The charger and cable that came with it are USB-C to USB-C. However, I need ANOTHER cable that will allow it to connect to the USB ports on the iMac. Won’t go into all the problems that created.
I‘ve been an Apple user for almost 20 years. I have too may Apple products to change to Windows based products. That said, I’m still disappointed with Apple. It seems the right hand doesn’t know what the left hand is doing. These hardware and OS changes are intentionally designed to force the consumer to send them money, not necessarily to improve their products.