I'm not sure I'd call a programmer "brilliant" if they cannot A) make a codebase simple enough for people to contribute to and B) handle the social parts of training someone to get good enough to contribute to the codebase.

Agreed. And this is the real miss of much of the Clojure community. There is a handful of amazing people in there pulling 90% of the weight of bringing noobs in to the language. And the rest don't even seem to notice their efforts. Little awards and grants here and there, yes. But the majority don't even care if the language has wider adoption or not. It works for them and that's enough. But many of the successful projects are toy or side project ones. A large number have comically minimal UIs... sub useful in today's world. Quite a few Clojure programmers use 2D languages in their day jobs, only bringing Clojure in for small parts if at all. All of this is a top down vibe. The core team has never meaningfully addressed the terrible error messages the language spits out because they are able to decode the problem themselves. Empathy or concern for noobs or wanting to grow the language seems a far priority for them. The same for the cryptic documentation, seemingly written for themselves at best. Very talented people, mind you... just not concerned with the things that would have caused adoption of their entirely unadopted language (percentagewise).