I've tried to use htmx exactly two times. Both times it just ran directly into a brick wall, because it's so limited and has no escape hatch where you can put your own logic. Their solution to this is their half baked new language, which isn't ready, a new language, and seems very much unclear. All they needed was proper hook points.
for client side scripting, I think you are talking about hyperscript, which is definitely more speculative than htmx, but I wouldn't call it half baked: a lot of people are using it successfully in production
a less-esoteric alternative would be to use alpine.js, which is similarly embedded but uses plain ol' javascript (and offers reactivity as well, hyperscript is more of a pure event-driven language)
I had this same experience. I thought it sounded like an interesting idea, but in practice I didn't think it lived up to some of the hype it often gets on HN.
I think htmx can do the same with built-in events---just not built-in. In fact you may even skip that one today because custom elements are wildly supported since 2020.