But with just a little JS you can have a full SPA. You don't need a virtual dom to manage some HTML tags. You don't need UI libraries to render a UI. You don't need complex state management hook flow whatevs to manage some state. You don't need routing frameworks to read and write the URL. And so on.

With just HTML and CSS you can get a very long way. And if that last mile is truly a requirement, DOM APIs and a few lines of JS (or TS) have it covered. Only when all that grows wieldy do you need npm, frameworks and complex trees of dependencies.