I know in practice it no longer is the case, if it ever was.

But semantic HTML is exactly that explicit machine-readable entrypoint. I am firmly entrenched in the opinion that HTML, and the DOM is only for machines to read, it just happens to be also somewhat understandable to some humans. Take an average webpage, have a look at all characters(bytes) in there: often two third won't ever be shown to humans.

Point being: we don't need to invent something new. We just need to realize we already have it and use it correctly. Other than this requiring better understanding of web tech, it has no downsides. The low hanging fruit being the frameworks out there that should really do a better job of leveraging semantics in their output.