I wonder if Astro will remain a simple static site generator. If it tries to add dynamism (and complexity), I think it will lose some of its luster. But if all anyone needs from it is a static site generator, it looks very clean.
A lot of the functionality and minimalism leads me to believe it was inspired by Svelte and other recent web tools. That said, the complete lack of JavaScript in the output seems to me like a stylistic—even ideological—choice rather than an established use case. Still, it's easier to make a simple solution elegant than a complex one.
Astro fits into its intentionally small niche very well.
You just described Svelte. All the JS minimalism and speed without sacrificing the power.