This is what I don’t get about HTMX, you can’t give a good experience without client-side JS, sure some developers might love it, but that shouldn’t be the yardstick.
Moreover, HTMX makes it incredibly easy to change the whole paradigm of submitting data. You can eliminate some forms entirely and just enable a series of individual questions/inputs/selects one at a time, especially useful when a single static form isn't always appropriate (multiple pathways, questions/options that are contingent on the response to a previous question, etc).
In my experience the UI flow and degree of detail for avoiding common errors is greatly improved.
There isn't one thing called "conventional React", there are all kinds of validation libraries on npm and many strategies laid out on Stack Overflow. https://stackoverflow.com/questions/41296668/how-do-i-add-va...
I think it's fair to say we have different opinions on good UX, no need to debate it any further
Its not a fit for every site or use case but more than any other front-end tool or library or framework, it has enabled me to actually realize the UI concepts in my head to the actual screen, and usually a lot quicker than I'd expect.