I think they meant most people aren’t building a high performance spreadsheet, not most people aren’t using a high performance spreadsheet.
Lots of people are building Blazor applications:
https://dotnet.microsoft.com/en-us/apps/aspnet/web-apps/blaz...
> not most people aren’t using a high performance spreadsheet
A spreadsheet making use of WebAssembly couldn't be deployed to the browser if WebAssembly hadn't taken off in browsers.
Practical realities contradict pjmlp's preconceptions.
Microsoft would wish Blazor would take off like React and Angular, in reality it is seldom used outside .NET shops intranets in a way similar to WebForms.
So, in other words, widely used in lots and lots of deployments.