Astro is, and should be treated, as a static site generator.
> Does it make it easier to throw in necessary JS (e.g. for comments)?
With astro you can combine html, css and js in a single file (.astro). You write plain JS (TypeScript) within <script> tag. There, you can, e.g. import your comment library, point to separate .js/*.ts file or write whatever logic you want for client-side JS.
See the docs for example JS usage in astro components:
Please stop recommending React as the de facto framework, we need some critical thinking back into front-end. HTML, CSS and JS are much better alternatives.