As someone who likes games from various periods (from Ultima IV to WH40K: Rogue Trader), I haven't ran into many games which do work on X11 and don't work on Wayland. Though I don't really have any of the old Loki games (I believe there was a port of Unreal Tournament?), so I might be missing out on the specific games which really lean into certain X11 features which XWayland doesn't support well.