Server-side apps cannot provide optimistic UI. No matter how you feel about it, they are limited in this capability compared to client-side apps. The user doesn’t care about the technology. For example, imagine a todo app that shows a new todo immediately. Or form validations that happen as soon as data is entered. That’s a superior experience to waiting on the server to continue interaction. Whether that’s harder to engineer is irrelevant to the user. We should be striving for the best possible user experience, not what we as engineers personally find easy or comfortable.

HTMX is cool. HTMX may fit your needs. But it’s not enough for providing the best possible user experience.