For just general web pages (as distinct from apps), it’s not common to actually require JavaScript. I know this because I’ve JavaScript disabled by default for the last two or three years, and it’s really not all that much of a bother.

The key thing here is that SPAs normally get some kind of interactivity benefits from being written in that style (though I confess they break things that the platform provides, by reimplementing them badly, at least as often), such as loading same-site links faster. But this thing doesn’t do that; it’s purely a projection, like XSLT. It should be done as part of a generator or server, rather than on the client side.