Is there anything I can do about this extremely vague block of data that’s taking up 30% of my phone’s storage? Mind you, this isn’t the operating system itself, as that’s listed as its own category.
EDIT: I tried (a) backing up to my computer, factory resetting, then restoring from backup and (b) setting the date years in the future. Neither worked, in fact (a) actually increased my system data to 34 GB! What DID end up working was updating my iOS from 18 to 26, which I had to do from my computer via iTunes since my phone was full. Apparently major system updates reset system data
I find it really annoying too. Unfortunately this has been a thing since the earliest apple devices. Back then it was called “Other” and not much besides the name change has improved. You’d think that apple would add a way to clean it manually but no, probably in the next decade.
With modern devices having a minimum of 128gb it’s not usually a problem in daily usage though. Only when it shoots up to many tens of GB then you can do the date trick.
If you temporarily set the date a few years in the future and wait a bit, the system will try deleting the cache. Just be careful of expiration for SMS chats.