For only a hobby, Blender is hard to beat. Also look a GameMaker.
XNA is mature but not dead. The reason why development on XNA has stopped is because it is mature. Games made in XNA will run for years in the future, so it is still alive. There are still many people using XNA, too.
MonoGame, an implementation of XNA, might be a better choice for the community support, and perhaps better implementation on a particular platform that you want to target.
Mono/ MonoDevelop are worth having a look. Unity 3D has some C# native coding, too. In fact it was derived from Mono.
Torque 3D comes with many art assets available for free or low cost. You would need to learn programming, but the community support is there.
For just a hobby, it is really hard to find better than Blender.