I'm running iTunes 12.12.2.2 and an iOS 15.4 upgrade just now happening. (If only the notice where I checked the box to 'dont remind me' would honor that request, but no it keeps popping up to remind me).
iCloud is not an option for some (our employers control the Exchange calendars and those calendars are never going to be allowed into iCloud for the foreseeable future), so via USB cable is the only way to sync my work Outlook Calendar with my iPhone in order to have a common calendar that also shows on my personal Apple Watch in the watch face... that watch face telling me when my next meeting is, is one of the huge reasons I use the Apple Watch.
If Apple proceeds with the removal of syncing by USB cable, then it breaks the usfulness of the iPhone and Apple Watch as a daily life platform rather substantially, and I may not further update down the Apple Watch path since it won't have my work calendar on it.
If the Apple Watch could work with two iPhones at once, that might solve it - as my work phone can have the work calendar, and my personal phone my personal calendar, and the watch then displays the union of the two. But I somehow doubt that will be possible, given that an iPhone can seemingly only trust ONE PC at a time.. because whenever I plug it in at work to sync, the phone asks 'trust this computer' to which I say yes, then when at home to sync my music, again 'trust this computer' to which I say yes, then back at work it again asks if I trust that computer... which I'd told it already it could trust. Hence only trust the last computer you authorized.
All of that bunny trail is just to underscore that the Apple software architecture seems to be headed in a bad direction because it is fundamentally at odds with how I suspect a substantial portion of the users need to use the gear. Remenicient of Apple telling its customers they were 'holding the phone wrong' back in the iPhone 4 time.