While I don't really agree, I do think that if one intends to work on a side project or a bootstrapped company, they need to do it in a way that is somewhat enjoyable for them.

It requires lots of energy to see these projects through, and it's hard to emit that energy on something that you don't enjoy doing. If using a less common technology is going to get you working on the problem enough to start getting some velocity, that may well be a worthwhile tradeoff (as long as it's not too out there).

The other thing to consider is that while a basic library supplied by a young language may suit your needs when you're starting out, larger ecosystems are likely to have more advanced libraries that have better performance characteristics, support more obscure use cases, etc., which will only become more valuable as one grows.