TL;DR: Apple's restrictions on what software you can install and "our way or fuck off" philosophy have doomed serious gaming on their hardware, and ARM is not great for gaming atm.
Think about it this way - Mac's software frameworks are not the primary focus for the vast majority of game developers (Metal was considered "do not touch" for the longest time for people not making mobile games), and Apple doesn't have an incentive or true motivation to try to move their frameworks more towards the standards on Windows, Linux, etc.
Also, ARM in general (while it can produce great results when software is tuned for it) is just not a good way to play games designed for x86. Valve is trying with FEX, but to do so on a Mac is sort of compounding the misery (translating the x86 game then translating the DirectX/Vulkan framework to something the Mac can use will eat your performance alive).
Additionally, the 100% self inflicted "Think different(tm)" problem on Mac for developers is the mandatory fees and the requirement to use Apple hardware to build and ship software for people to use in the "official channels". That might be something a company like Adobe is willing to stomach, but not most game developers.
Addendum: Also Apple's history with shitty cooling solutions and voltage limits means the CPU/GPU probably wouldn't be able to perform to their greatest potential anyway compared to a traditional desktop pc.