It's really fast, you can edit it with Notepad, and you can probably saturate your bandwidth with a consumer level PC.
It's fluff because, well, our expectations are so unbelievably low. By the time you've bolted on every whizbang dingus leveraging four different languages (two of which are some flavor of Javascript), your twelve page site takes a couple of minutes to compile (what?), and it chokes your three load-balanced AWS compute nodes.
Web applications are hard. I get that. Web sites? They were, by design, incredibly simple. We make them complicated for often unclear reasons.
I appreciate what the Astro folks are trying to do, and it's very clever. But your basic Web site need not require freaking npm in order to "return to the fundamentals of the Web".