Before devs started experimenting with client-side rendering, all sites' content was amenable to the same set of tools. Now there are more and more services with broken frontends and unique APIs which are incompatible with everything else and aren't even stable—when you can rev your own client js instantly, you don't know or care whether any other clients broke. I'm stuck using only one client (your js) that works at all and I can't fix it, which is almost everything that client/server got wrong the first time around. It's not impossible to carefully implement a stable form-compatible API in common with a bunch of similar sites, but I don't see it happening.