Sharing files between apps and file management in general on iOS is atrocious.
I assumed this was a solved problem before Windows 98 (first desktop OS I used), but Apple cannot get this right 28 years later.
Funnily enough, Windows 98 is the first OS I remember with a sharing menu (“Send To”, which is memorable to me because the official Russian localization of it was suggestive of an obscenity). It seemed so pointless back then.
At least there is a Files app these days, and many iOS apps interoperate a little bit with “Files”.