The difference of Blazor compared to a "classic" SPA (for example React + JSON API) is:

Blazor Server: On a broken/poor connection there is no interactivity anymore

Blazor WASM (=SPA): Keeps working when connection is lost, but everything is sooo slow

classic SPA: Keeps working with lost connection and is fast.

Last year I created a Blazor WASM app[1] to get familiar with the tech. It was a game based on the board-game from the 60's called "Acquire". Although it's using the WASM hosting model, I did use SignalR to facilitate the real-time game play between players. The "practice" mode against the crude AI is entirely WASM and can be "played" as a PWA completely offline. I had intentions of finishing this out, but I got far enough that I learned what I needed to for now. I felt like it was pretty good considering it's probably less than 40 hours of work and I'm a mobile/desktop dev not a Web dev.

[1] https://acquiregame.azurewebsites.net/

> Blazor WASM (=SPA): Keeps working when connection is lost, but everything is sooo slow

Why should it be slow? Once Blazor WASM is loaded, it doesn't need a connection to the server anymore.

.NET runs in WASM around 20 times slower than in the server runtime. The application is just slow, not the network.