This sounds like a Remix problem more than a React problem. I really enjoyed the ideas behind Remix actually! In fact, I found that having both server and client code in a single file (a-la Next.js) made me super productive. And nowadays I bet it pairs well with LLMs due to having the full vertical slice available in the agent's context.

I really wanted that framework to take off.

But that community is straight toxic... I have not seen a more toxic community than the React Router community. It's one of the reasons I stopped using Remix. React Router 7 is actually pretty cool; I recently built a prototype on it and was surprised by how well it worked. But I know I'll eventually need some kind of support and feedback, and I can't imagine engaging with those devs/that community again...