Guile Emacs already is fully usable, and has been for a while, but because basically nobody is using it, it bitrots right quick and there's nobody hyping it up; which results in nobody using it and it gradually withers away until the next push to revive it.

Speaking as one of the mostly satisfied Overleaf users: I mainly use its Git sync feature and edit locally in Emacs.

But many collaborators were not using version control in the first place, which meant that Overleaf was a huge step up from our previous workflow of emailing manuscript_v12.tex around and waiting to receive edits.

Not to mention the issues we previously had trying to get it to compile equally on every machine, where coauthors use different TeX distributions with different packages available and different versions installed on different operating systems.

Overall, I think Overleaf struck a pretty good trade-off between being usable by both techies and non-techies. My main pain point now is having to open the web browser to create or clone new projects, which I don’t do that often, but I wish they had a command line interface or something for that.