The mystery of why .NET got so many things right is simply that C# was built several years later by the exact same Microsoft engineers who had previously worked on extending Java, giving them a perfect blank slate to fix the architectural flaws they had already encountered

Second mover advantage.

virtual thread instead of async/await is a counter example.

Java is more used than C#, they can wait before delivering a new feature (given their leader position) but cannot deliver a flawed implementation that would stay in the language forever. Glad to have virtual threads and the backward compatibility that comes with it instead a Async version of sync methods + async and await keywords all over the code and Task as a return type in my interfaces methods to allow implementations to do non blocking I/O calls if they need.

I use Java and C# and appreciate them both.

> giving them a perfect blank slate to fix the architectural flaws they had already encountered

and then they make everything nullable by default in c#...