I am an Emacs enjoyer. My biggest issue with Emacs is that development is still done via a mailing list and patches. I wish they would adopt a Git front-end (web UI) workflow.
https://git-send-email.io/ has a great tutorial for getting started.
There's probably also a lot of emacs contributors that use emacs as their mail client that would be disrupted by replacing it with something web based.
Git was made for email. Needing a separate service for it is mostly cruft, when you have mailing lists. Yes, github has mass appeal, but a lot of software has been written with just email collaboration.
As for attracting low-quality contributions, I don't think they matter. People who use Emacs and depend on it will contribute. Interest in Emacs has increased and so have the available features.
There's a decent, loyal user base, importantly not the free-loading, entitled kind who water it down; they're like-minded, appreciate the philosophy behind it, don't mind tinkering with some LISP here and there, contribute their creations as answers or packages, and above all form a nice community helping each other.
It is so discouraging that I stopped working on the Emacs core [1] altogether: your contributions won't be acknowledged at all, even if someone volunteers to rewrite your code from scratch.
[1] I've been hacking some GUI-related features, but I'm not motivated enough to complete them. I also tried to write patches for my bug reports, but alas, my "CA-free" quota is already used up.
The further I get into "emacs for everything" the more I appreciate using email for everything.
Gitlab has some threading support but not very good one.