it does, however, have an extensive event model to hook into, including pre and post request processing:
https://htmx.org/reference/#events
as well as an extensions API:
https://htmx.org/extensions/#defining
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)
<div x-html="(await axios.get('/some/html/partial')).data">there are a large number of events
and the extension mechanism has enabled a diverse number of extensions:
generally I consider htmx to be on the high side of JS libraries when it comes to events and hooks that can be used