"I rather use C++ than being stuck in .NET 3.5, without any more modern C# goodies" - I use all modern C# features with XNA - what is the issue (except for async/await maybe)?

"I guess one has to decide if they want to make a game or a game engine" - exactly, but there should be a choice. XNA being a framework rather than engine provided such a choice in a high-level way.

> I use all modern C# features with XNA - what is the issue (except for async/await maybe)?

The libraries are also important and they are stuck on .NET 3.5 offerings.

Another problem is the old version of Mono they are using, which doesn't not have the JIT and GC improvements of more recent versions.

This is what I was able to gather from online sources, when wondering if it was worth the time and space to install it.