Hi All,
I have been a long-time lurker and finally signed up
I was having the same issue with my Iphone 14 pro max with 256gb with the system data memory being filled to the point I could not do anything.
A re-boot would work for a day or two but went back to square one - I also did resets ect.
But! What seems to work was deleting the Apple Tv App, Rebooted the phone and the storage went to 6gb from usually 20gb, left it a few hrs re-installed the TV App and all so far all seems to be good and has been at 6gb for a few days and my battery seems to be better as well.