A problem with HTMX etc. is that you are then locked onto another ecosystem. They complain about how bespoke eg React is vs. hypertext, but you are still relying on some JS library (their htmx) to get what is missing from w3c html.
The main difference i think is more between a declarative / markup language vs. a programmatical one.
But it seems like declarative here also means limited to what is built in. If you need to go beyond that it bends the paradigm to the point of breaking?
And there is so much custom nuance required in order to get actually good UX that i'd lean towards a non declarative js thing probably.