C# is a great language, it's now very modern and has the best parts of Typescript, while leaving out the bad ones.
It's also extremely fast and multi-platform.
It also doesn't have the fragmentation that Java or JVM langs has.
And it's also open source nowadays. I think Sillicon Valley hasn't caught up with those recent changes, I bet more startups would be using C# if they knew.
I really like C#, but I wouldn't go that far - unions are at least on the horizon, but I've sometimes come to miss the power and flexibility of TS's structural typing...(And so has Hejlsberg, apparently, seeing his reasoning for choosing go over C# for tsc :) )
I also write lots of Typescript, and the furthest I go is to use 'Omit' and other utility types, but already feel like it's too much.
The overhead argument seems fairly objective to me - clean code with low coupling in C# et al. requires separate definitions of interfaces and implementations, explicit conversion methods between compatible interfaces etc. This adds up over time and makes refactoring pretty annoying.
The tight coupling happens when people don't bother to define interfaces. Suddenly I have to couple class hierarchy to classes from unrelated modules, all so the compiler is happy when I pass structurally equivalent data. To keep my own modules clean I have to add yet more interfaces, conversion methods etc!
It was more related to the fact that the existing TS code was more easily ported to Go, and also .NET AOT wasn't mature enough at that time. Structural typing has its own problems. I'm personally not a big fan of it.