>A simple LINQ expression can be passed around an translated on the fly by various providers. The same expressions can be translated to Sql, Mongo, regular IL, etc.

The same can happen with a simple abstract expression in native syntax (in fact tons of tools in all languages that do that). LINQ just gives you a standardized built-in DSL for that -- but nothing you can't build yourself with the language's main syntax. Heck, LISPs have been able to do the same shit for half a century.

>Last time I checked neither SmallTalk or Haskell are taking the world by storm...

Yes, they only made a dent with the smarter developers.

Still, C# isn't taking the Linux world by storm either, and it's nearly irrelevant on mobile too, so there's that.

>Haven’t Java proponents been claiming Java was going to be fast for over two decades?

Java has been fast for over 15 years now, so not sure what you're getting at here. Faster than C# as well, so there's that too.