Depending on the application you can get extremely far with just using HTTP requests to an API for anything business logic related. A lot of apps over complicate themselves by trying to force a JS framework on the front end with no benefit to the user. I seem to prefer using non-SPAs these days over SPAs because very few places do them well. Google being a terrible SPA developer.

- Edit - I forgot to mention Elixir's Phoenix has LiveView which is similar to Server Side Blazor.

I have a data web-app heavy app where users will routinely view over 300MB of data in charts and photos. In this context, .net runtime is insignificant. In fact, you could could argue such data intensive applications should be native and use local storage. Lastly, the browser with cache .Net runtime, and won't download it very often.