In some ways, React on the server is worse than PHP. Server-side rendering of client-side code adds a ton of complexity, and can even introduce performance issues that must be worked around before the app can be launched (e.g. needing to pre-warm caches).

I'm sure there are valid uses for server-side React, but at the end of the day, using server-side languages such as PHP or Rails (or even rendering pages in Node.JS if you like JavaScript) can be much faster and simpler.

I say this having been involved in an app rewrite that used Remix. The project has taken 2 years (and still isn't quite out), and the engineering leaders who made the decision have agreed that we probably could have rendered most of the pages in Rails and used JavaScript for a limited number of things. With that said. I am hopeful that the project will work well when all is said and done, but there were a lot of tradeoffs associated with going to a server-side rendering framework.