C# and .net are one of the most mature platform for development of all kind. It's just that online, it carries some sort of anti Microsoft stigma...
But a lot of AA or indie games are written in C# and they do fine. It's not just C++ or Rust in that industry.
People tend to be influenced by opinions online but often the real world is completely different. Been using C# for a decade now and it's one of the most productive language I have ever used, easy to set up, powerful toolchains... and yes a lot of closed source libs in the .net ecosystem but the open source community is large too by now.