While I'm also less than enthusiastic, I would counter that MS open source has been very good overall. Silverlight was never floss. .Net Core has seen some really great strides and it's a decent option.
I still prefer node and react, and for web assembly find rust+yes more compelling. I wouldn't about C# as an option on the backed, I just don't like Blazor.
When I speak about C# open source being dead, I'm comparing it to NPM. NPM alone is a million times more robust. Right now, Blazor open source contributions are laughable. I don't feel that will change much. MSFT has been sleeping while they built Azure. They are 10 years too late.
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