If we write HTML that has no content just the head title body and metadata with script and style elements to external style and script is it really a hypertext markup language at that point?

I think I get your meaning, but I'd guess you're referring to libs like React which only deliver a barebones "document" as actual HTML to bootstrap a script-generated page? In that case, you still have to generate & render HTML at some level to do anything useful on a web page.

I've come to think of HTML, CSS, & JS as low-level languages like Assembly or C. Rarely do you need to delve into those unless you're doing something really close to the metal. Yet, even React's JSX ultimately outputs real HTML - just not handwritten HTML.

I haven't written plain/raw HTML, CSS, or JS in probably the last decade. But they're still intact & are basically the only markup, styling, & scripting languages that browsers understand. It's just that we have much higher-level languages & tools now to generate/preprocess them.