Also, "The .NET 5.0 core framework libraries have been annotated to indicate what works in the WebAssembly runtime, so developers now get a warning in the code editor when attempting to call an unsupported method." from https://www.theregister.com/2020/10/15/microsoft_emits_net_5...
Blazor has two separate modes, 'Server Side' and 'Web Assembly'.
What you're describing is the server side mode.
The second mode, called Web Assembly, compiles your code to WASM that is executed in the browser.
https://docs.microsoft.com/en-us/aspnet/core/blazor/hosting-...
Also, "The .NET 5.0 core framework libraries have been annotated to indicate what works in the WebAssembly runtime, so developers now get a warning in the code editor when attempting to call an unsupported method." from https://www.theregister.com/2020/10/15/microsoft_emits_net_5...