Yeah, this is a big reason why the Polymer project is moving away from a bespoke expression syntax and control-flow in HTML, ala Angular and Vue, to using just JavaScript with lit-html.

But not only does it mean that users don't have to learn a new language and concepts, but it mean the maintainers don't have to develop a new language and all the corner cases, feature requests and bugs that come with it.

And in the case of lit-html, you also eliminate compilers completely because there's also no non-standard markup-in-JS syntax.