Google keeps breaking it. It's a shell of what it once was.
Discussion
What did Google do to it?
Did they change the code?!
Is it the Android WebDAV implementation and other OS stuff you're referring to?
They keep adding restrictions that break essential features. For example:
https://help.nextcloud.com/t/autoupload-no-longer-deleting-files-from-source-device/213411
Thus is fucking stupid. So it is Google code. Since when do they own the damn app? Do they make changes to the server or desktop client, or is it just forced changes to the Google Play app?