Agreed, Stimulus is so simple that there's almost no prerequisite other beyond a basic understanding of HTML and javascript, both things that any "React developer" and even most "backend" web developers should already have.

Maybe I'm biased but I feel like rails + stimulus makes it incredibly easy for anybody with any kind of programming background to grok the entire project, and maybe you can reconsider even even having dedicated "frontend developers" at all. I know that specialization is a thing, but it's just so easy to be a "full stack" developer on such an app that I think almost anybody could pick it up.