Samba has never been about file sharing over the internet. The project has been about cleanroom-reverse-engineering specific MS technology. To start it was NT4 authentication domains, then printing services, along the way SMBv1 (commonly incorrectly called CIFS btw), then SMBv2 v3.x, and then in 2012 Samba Active Directory.

In no way has it ever been about a functional alternative to something like Nextcloud. It's been about services primarily for LAN functionality, not stuff that should be going over the internet (mostly for security reasons).

So your expectations really don't align with what Samba has ever been about.

Source: I professionally support Samba for businesses.