Native dropdowns have much (much!) better UX and accessibility than most custom dropdowns built with JavaScript. Same goes for native form validation. And there are many more examples. Using JavaScript does not necessarily improve UX.

Use the platform where it makes sense. Extend it with JavaScript where needed. Make it work for everybody and make it better for capable browsers. That is called progressive enhancement. OP did not say that you may never use JavaScript. Just be mindful about it when you do.

You can say the same about computers in general. No computer is preferable over having to use one.

When someone has just barely crossed the "hello world" stage, I don't think they should be thinking about asynchronous XHR requests, or be pulling up user experience research to find the optimal shade of red for making input validation errors appear less aggressive to middle aged women with a bachelor degree in communications who are part-time employed in marketing.

Let's start with getting data from the form to your back-end, and once we've got those must-have basics down, then we can start introducing the nice-to-have bits.

I consistently have a more pleasant time with the well-designed, minimal JS websites (which are now a rarity) than even the better designed websites which heavily use JS. And my job is allegedly to 'improve' the internet with more JS.

See https://remix.run for a clear demonstration of "best of both worlds".