The lack of transparency in iOS really frustrates me, perhaps because I grew up in a time when computers didn't try to shield the user from every process. For example, not being able to edit file extensions in Files, and not being able to force a save in iA Writer — hell, even having a save/not saved indicator (eg as macOS has with the black dot inside the red button) would be more comforting.
I'm entirely disinclined to "just trust" that my files are syncing and that nothing will be lost. That's not how computers work.
File management and the extreme abstraction from the file system (even with Files) is what stops me from buying an iPad Pro. Love the device, really don't enjoy the OS.
Android would be lovely, but for the privacy concerns (and the lack of any decent tablet).
So the answer would seem to be a MacBook. But it's rather obvious, in a fine dining restaurant, that I'm writing a review if I take a MacBook out. And would look rather odd.
To conclude, then, I must continue to suffer.
(iCloud Drive is not an alternative to Dropbox for me, at least until it goes cross-platform.)