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.
One of my hottest takes is I liked vanilla D3 better than what it became. Taking out trade and economy made all items feel worthless. Getting a primal ancient legendary just didn’t hit like finding a high end weapon in vanilla, or a high rune in D2.
the real money auction house was a mistake that ruined drops but I’m right there with you, I’d play day 1 D3 over the current mess if I could.