I haven't followed game development in a long time, but has the industry moved to C#? I thought C# was limited to Unity and everyone else was still using C++?
Unity uses their own AOT compiler IL2CPP that translates C# code to C++. Mono is an option in builds, but most projects are using IL2CPP nowadays and have been moving to .Net core. Although C++ is king, C# has quickly caught up to be a close 2nd. Unity is used to make 50% of all mobile, pc, and consoles games (according to Unity https://unity.com/our-company).
The biggest player that uses it is Unity, but even they have their own special fork of Mono to get it to play nice.
Full Disclosure: I work for a Microsoft/Xbox Studio.