> And now it's even less scalable to larger sites

And how is 20MB js SPA with 20 wss connections more scalable?

I've see too many react/vue projects bundling everything into a single main.js file even pages I never click. e.g. some crazy map or graph module. Is there some magic in webpack to make sure the needed functions gets executed in "eagerly" fashion?

Or does json provide streamable parsing capabilities?