But for now it doesn't work as well as a classic SPA architecture. The server-side mode works not very well on poor connections (mobile), and the client-side WASM builds are extremely slow. Especially on first load, this takes seconds.
Blazor may be well suited for Intranet apps already, where quick&cheap development is very important, and connections are fast and stable. Blazor Desktop is an example for that use case (no latency between frontend and backend).
For internet apps, something like Gmail or Instagram, it seems to be not very well suited. Especially not for websites with interactive content, for example a comment-box inside a blog. Nobody wants to wait multiple seconds until the content is responsive, or the "reconnecting to server" overlay disappears