i think the biggest point is that it's hard to find developers in a special niche even if it allegedly offers productivity gains, this is negated by increased costs.

clojure was cool, I used it mainly for datomic, but the gains really dont justify relying on public slack channels and mailing lists to hire and find devs.

I really see this from an economic point of view. I could be mistaken based on my own experience dealing with clojure and datomic in particular. I'm just not sure the gain is there anymore as other databases built on conventional tech stacks increasingly more or less take away the gains.