I assume "jQuery" here is being used as a metonym for the old frontend style where you would use the jQuery AJAX and DOM functions to query HTML fragments and swap them in. This is only really related to jQuery in that it used jQuery utility functions; under modern conditions you would just use fetch() and querySelector() etc to do the same thing.

It's true that the core concept of HTMX is very simple, and you could probably reimplement any given particular use case in a few lines. However, it is in fact a big advance over the manual HTML-fragment style, precisely because it abstracts over the particulars. Standardizing on a particular, good design is an important benefit even if the functionality of the code is easy.