Personally, I don't think Blazor is really finished, I wouldn't use it in production. It's more of an example of what can be.
Ultimately, I don't think 5MB blobs are all that bad for web applications that need the enormous complexity these libraries provide. Classic Django/Symphony/Spring Boot with some CSS animations and Javascript glue can work perfectly for the smaller apps. For things that aren't applications, you shouldn't need any framework at all, websites can/should just be static files to make everyone's lives easier.