The web is human-accessible content hosted at stable linkable URLs. If you send fragments of ad hoc data and rely on just one piece of code that might be able to reassemble them into something usable on a couple out of all browsers, that's not a useful contribution to the web, it's merely a client/server app which tunnels yet another nondisclosed protocol over HTTP. Somehow we ended up with a new crop of devs who don…
I think the web can still be human-accessible content hosted at stable linkable URLs. But now the question is, can we require the user-agent to support JavaScript in order to show the content, like we already require it to support HTML.
If your documents are complete (no js-generated extra requests to get actual content) but your default rendering is flaky without trusting your js, I consider that shoddy work but not an existential threat to the web.