From my first glance, it is not really. Has its own templating syntax, its own file format etc. With NextJS static export I only have valid react/tsx and would not want to introduce a framework-specific language. Also could not easily find something about the routing

While Astro does indeed have its own type of components, it also supports React, Solid and a host of others. So transplanting your current tree of components in, adding the React plugin and saying "GO" is likely a fairly straight-forward project. I moved a previous static site into an older verison of Astro with very little trouble.