> How easy is it to hire people with experience in this?

When NoRedInk switched to Elm, Richard Feldman, who was asked about whether this impacted their hiring experience in any negative way, said that on the contrary, hiring had never been better, because although the pool of candidates grew smaller, their quality (either prior experience of working with type-safe functional programming languages, or enthusiasm for learning them) got higher.

When Alex Russell announced several openings at Microsoft for development of design systems with web components, and certainly no react, he said this attracted a lot of really strong candidates.

I am not saying that a good web developer should be able to pick up any exotic language, such as elm, or purescript, or rescript, or clojurescript at no time; but what I am saying is that as far as web frameworks are concerned, they shouldn't be a criterion for hiring, and are unlikely to become an obstacle to it.