Comment by dsego

Why not? You can have server side routing that returns the page and then react then takes over and hydrates a small part within the page or the complete page. A similar approach is used for the islands architecture, and you can even combine different frontend frameworks for maximum flexibility, e.g. developer preference. You can decide to load your frontend libraries lazily or as shared scripts so they are cached and only take up some bandwidth on initial load (a couple of kB minified and zipped).