I’ll credit both sides with the stubbornness. Apple had many years of poor integrated GPUs (arguably Intel’s fault) and even mediocre dedicated GPU options (due to a rift with NVidia).
Apple also fully dropped 32-bit support, breaking a lot of older games that had been ported to Mac on Steam.
Even Windows running on ARM has emulation for 32-bit x86 apps.
On Valve’s side they gave very little love to the Steam client on Mac and didn’t bother to update their own games (Half Life, Portal, Counterstrike, etc) to 64-bit to keep them working on Macs.
The biggest thing that has changed is now Apple ships much better GPU power even in its cheapest Macs. They still aren’t equivalent to dedicated gaming PCs but are plenty to run a huge library of casual and older games, if only there were a convenient and well-maintained path to running them.