I'm sorry, isn't the goal of web frameworks, including in this category Django, Next.js, Phoenix, Laravel, Nuxt.js to respond to HTTP requests and present users with an HTML page representing a document or a more complex web application?

> because JS does 99% of what anybody needs a web server to do

Brainfuck is Turing-complete and does 100% of what any other language can do as well. I stand by the fact that having to "know" only one language is great in theory, but in practice it's not. Node and client JS/Webpack are a leaky abstraction it's not very hard to get yourself cut with. In non trivial modules, you'll find it hard to be able to use the same code verbatim on the client and the server. Then add the complexity of server-side rendering, serialisation/hydration, React suspense, code that mysteriously works only when server-side rendered or viceversa, etc. and you'll ask yourself "is this really worth it?"