I can't comment on react, ssr etc, but one thing that I've been wondering about as a php developer is why even use custom elements at all, let alone web components?
As you say, why not just send normal, raw html down the wire?
I suspect I'm missing something though. Perhaps it's to do with being able to encapsulate/isolate each component's css and js, such that if you mix components across projects (or have different teams working on different components), their css and js have no chance of conflicting. Even if you are a single team, it would still, presumably, allow you to import existing components from external libraries etc...
Well, even in a server-side PHP app, you have some client-side stuff for better interactivity and a smoother experience. Custom elements let you encapsulate this stuff. It's really not necessary, but if you want to reuse or redistribute them, they are pretty nice and self-contained (mostly).
As you say, why not just send normal, raw html down the wire?
I suspect I'm missing something though. Perhaps it's to do with being able to encapsulate/isolate each component's css and js, such that if you mix components across projects (or have different teams working on different components), their css and js have no chance of conflicting. Even if you are a single team, it would still, presumably, allow you to import existing components from external libraries etc...