If you meant mandatory in terms of the actual medium requiring it, I can only hint to interactive applications, aside from that I don't think it would actually be mandatory.
All of those can be rendered server-side if needs be, and in my experience, can actually lead to a superior browsing experience compared to plain server-side served HTML. But it has to be done right.
Gatsby + Netlify with a CMS-as-a-service like Contentful or Prismic will lead you to a good result. We made e.g. https://fox-it.com/ using that, its back-end is Wordpress but it's drained empty to rebuild the website. Note how it works without JS, the dropdowns don't work but they fall back to full page navigation page. Note how with JS enabled, all the content shows up instantly. This is how it's supposed to be done.
Absolutely the can, yes. I wasn't saying they couldn't. I just answered the question. And those frameworks really introduced the idea of loading JS in order to load content to the broader masses. Things have evolved, sure and it can be done right, but nonetheless, those frameworks are a reason to force JavaScript on the user.
Gatsby + Netlify with a CMS-as-a-service like Contentful or Prismic will lead you to a good result. We made e.g. https://fox-it.com/ using that, its back-end is Wordpress but it's drained empty to rebuild the website. Note how it works without JS, the dropdowns don't work but they fall back to full page navigation page. Note how with JS enabled, all the content shows up instantly. This is how it's supposed to be done.