I consider this an alternative development approach neither better or worse than what it is trying to replace. The winner in recent approach, imo, is Remix Run.
The contract of the web is that while the client-side language in use may not be up to the discretion of the developer (recent evolutions in WASM notwithstanding), the server-side language/framework/OS/etc. can be literally anything which speaks the protocol of HTTP/HTML/etc. JS frameworks for years have repeatedly broken that contract with the claim that we must accept it for…well, "reasons". If it turns out most of those reasons are bupkis—more a matter of preferences than requirements—then we must stop breaking the contract. JS as a server-side language should _get in line_ alongside all the other languages out there.
Why privilege it if we don't need to?
This is being too reductive of the design of Remix. It is closer to traditional web applications in handling form submissions. There's no client-side state management needed for those use cases.
Whether it's the "winner" or not, really depends on use case, but it is decently different than a traditional SPA.
At least in some sense?
That said, using React on the server side and forcing you to run JS on the server is not my cup of tea...