I'm genuinely surprised there hasn't been any significant effort made to make it more readable.

Quite the opposite. They've tried to make it better, and in turn, they've made it worse.

They used to have a pretty straightforward Linux file structure, and you were expected to put things in the external Pictures folder. And downloads went to the external Downloads folder. Back then, internal storage was small and SDs were large, so apps couldn't really afford to store these things locally and the SD structure was well enough defined that it was pretty clear where pictures would go.

Now, Google has pushed against SD cards. They also started requiring more permissions for external storage. They've added some "documents" APIs that were supposed to make it easier to tag/find files, but it's a tangled mess and most apps don't touch it. And they've rewritten their storage model multiple times at this point. If you're writing a new app, it's unclear which model to even follow anymore because Google has created a giant cluster fuck of options and paradigms.

Google is actively making this problem worse and worse. I wish they had never tried to "fix" this in the first place.