Every time I attempt to use HTMX and backend-rendered templates because it's "simpler", in the end I always end up doing JSON APIs and something like Svelte. Because all the "simplicity" explodes in complexity 5 seconds later, and it's very user-hostile with the constant reloads.

This blogpost affirms it

I think it is right to call out HTMX as being a wrong approach for custom form elements. Try a progressive enhancement approach with something like Turbo, where you can still write JS as needed. This wizard could have been more elegantly implemented by removing the server requests for each step and just showing/hiding fieldsets on progression.

User hostile? Constant reloads are exactly what htmx gets rid of–that's the whole point.

If you mean developer hostile–sure, reloading the backend server can be annoying if it compiles slowly, like say Rust. I would say, pick the right tool for the job. If you're going to use htmx, pick a backend language that compiles and reloads very quickly.