I wish there were a way to use static site generators written in languages other than JS but still use JS features like JSX. I really dislike most templating languages because they are just hacks over a real programmatic way of composing content (via functions that return content). In templating languages, it's more like straight substitution of content.

It's similar to macros vs actual functions in something like C++. Sure, you could write everything in macros but why not use actual composition?