The first game that comes to mind for me is Civilizations 4. I’ve probably spent hundreds of hours playing but after getting used to 5 and 6 I have a really hard time going back. Going back and forth between 5 and 6 I need to rethink some strategies but with 4 I feel like I need to rethink everything. I don’t know if it’s because of the tech tree layout in combination with the civics system, things like unit stacking, or maybe just a bunch of little things but it takes me a while to readjust.
Yahhhh RMAH was a good idea in theory. In practice, having RMT harder to access and shadier works much better than building your game and its drop rates around an actual auction house. When I was young I hated RMT so it feels weird saying that.