Not a great article. The big thing is JSX; it's so much more pleasant than building UIs with the document/element api.
Building DOM is not a hard problem at all. Yes, it's more tedius with Vanilla DOM. But that's not a hard problem.
Hard problem is making it fast, reliable and predictable.
When the whole premise is flawed, JSX or not, does it really matter if there is a better or worse way of misusing a technology not meant for UIs?
Leave HTML and JavaScript to Wikipedia and other hypertext document libraries.
Unfortunately, WASM is not there yet, but people are trying: https://platform.uno.