Those stats are pretty meaningless. How many of those websites haven't been updated in the last 7 years? Not that there's anything wrong with that, but the decisions they made a decade ago aren't necessarily still the best ones today.
How is that meaningless? It seems that web users of the site at least find it acceptable and aren't complaining enough to the site builders that they feel the need to change the website. AKA the website is standing the test of time. That's kind of a huge bonus when it comes to saving money and time to the website maintainers.
The point is that if you were to start building a new website from scratch today, the best tools for you aren't necessarily the most widely used ones. You have the option to start with a clean slate without any baggage. There are no upgrade costs. There are no customers who will get inconvenienced. There is no inertia. You are in a very different position than someone who has a website with millions of lines of jQuery already in use.
Even with a clean slate, there's immense value in choosing something that you already know to be a tried-and-true approach - i.e. in choosing "boring" technology¹ instead of trying to be at the cutting edge.
Now if exploring the cutting edge is a goal of yours in and of itself, then by all means blow some of those innovation tokens on the new Reactangular.ts hotness. For a lot of projects, though, the goal is to get something out the door as painlessly as possible; jQuery and plain JS have (for better or worse) been the tried-and-true "boring" approaches, and HTMX (from what I can tell) seeks to be the similarly "boring" choice.
Obviously right now HTMX ain't the boring choice (because it's still pretty new), but a decade from now it could be. Having used it in a couple pet projects recently, it already does feel pretty boring (especially since it goes hand-in-hand with other boring strategies like "just use SQL" and "just use CGI scripts" / "just use classic MVC frameworks").
