Any Mac that has to use an Intel GPU is going to struggle, no matter how old/new it is. This is partly because Intel iGPUS don't implement most of the features needed for the double conversion layer that is DirectX to Vulkan to Metal (dxvk running on top of moltenvk), and partly because Apple's Intel Graphics drivers are....not great.

Intel Macs that have a decent AMD GPU in them should still run fine and are where you can get the best performance in general, although Apple Silicon has shown itself to be pretty good. The recent changes in FFXIV as of patch 6.4 included a new Wine/CrossOver wrapper, which updated the base with better Apple Silicon support.