I am also frustrated by the current development situation.
I think it would be good if we could add at least one active person other than Oy to the developers. I would like to try this if I was allowed to, but I'd be equally happy to have any other active person in that role. That person should be sufficiently reachable; this is currently a big problem we have in Teeworlds development: No active development discussion happening, developers rarely meet on IRC etc.
I think we immediately need to improve the experience for new developers, as it is currently very hard to get a working Teeworlds build out of the source code IMO. When I compiled the release artifacts for the latest release, I had problems on both OS X and Windows, where the build only worked after applying a few tricks that someone new to Teeworlds development probably wouldn't think of. This hurts the community, as many potential developers might go away. Another thing that we need to improve on is response time on pull requests. When I opened an easy pull request on some repository on GitHub and it was responded to within one day, I was definitely happy about that. Compare that to pull requests that have been lying dormant for over three years on the Teeworlds repository, like #1086, essentially without response from an official developer.
Thanks for creating this topic, unsigned char *, I have also thought about creating one for a long time. Btw, I think this is still the same situation as back when this topic was last discussed: Landil's post, Sushi's post. And it's been five (!) years since then.