Well React doesn't come by itself. You need a router, probably some way of managing shared state, bundling, compiling your TypeScript, and 7 other libraries
The more stuff you add on the harder everything is to understand, and the less stable your app becomes until suddenly you need specialists for every piece just to keep things chugging forward. Everything needs greasing and maintenance over time..
..and then in 4 years the React team decides "oh you know what the way Svelte is doing things is actually way better.. we'll need a re-write to integrate their ideas". Now what?
"that wouldn't happen! so many businesses depend on React!".. uh they have no obligation to make things compatible with whatever you've built. They're not working for you. What happened with AngularJS? Vue 2?
Hotwire is easy to understand (React "just renders it" is a massive oversimplification)
If Hotwire rewrites? I create a private fork and continue on. Who cares
If I want to tweak how Hotwire works cause it'll benefit my app specifically? I do it myself
I'm not against adding complexity.. but if you care at all about longevity and long-term productivity then adding React really needs a tonne more consideration than it gets
I think we fundamentally agree that we want to be careful about adding complexity to a project. Funnily enough there have been many times where I really thought Hotwire equivalent would have cut down a lot of complexity. I've also actively looked at web components at work and for hobby projects to see if we could make/keep things simpler.
But maybe I'm biased because I've been working with React for a long time, I don't find it too daunting to manage dev tools around React. When React was young, I remember that there were _a lot_ of ecosystem churn but now it's more-or-less settled and I don't think it's too bad.
I don't know how Hotwire works that well as most of my experience is around Elixir's LiveView, but at least for LiveView, there is also quite a bit going on under the hood to make it performant for large lists and to handle error states gracefully. And I (maybe incorrectly) assume Hotwire is similar, so I feel like it may not be not as simple as you say. (Edit: it is simpler than React though!)
It also doesn't need to be all or nothing. I've become a big fan of progressive enhancement or an islands approach. Default to SSR and scale it up as needed