I'm saying if Apple wants their Macs to be considered as viable main gaming devices down the line
Well that's the real question, isn't it? I don't think Apple has ever
wanted to position the Mac as a "main gaming machine."
It certainly
can be a gaming machine; a very capable one, in fact. But they're not going down the rabbit hole of chasing specs to try to compete with Valve, Lenovo, Asus ROG, Nvidia, AMD, Microsoft, Sony, or Nintendo, for a relatively minor share of the entire gaming market.
They have demonstrated that their focus is on mobile and tablet gaming, because it's a much bigger market, and more profitable for them. And that's fine!
if Apple wants to say a Mac is a good alternative to a Steam Machine, it better play a decent amount of the same games from the same stores.
And yeah, if they
wanted to do that, it'd be a logical step. But they don't.
Now, if
I were Apple, what
I would do is focus on integrating emulation into Apple Arcade, and beating other platforms on ease-of-use.
I have a Retroid RP5 Android handheld. It's designed for retro emulation, running on a Snapdragon APU. It's good! But setting up all the apps, frontends, special folders, tools for auto updates, sideloading stuff, finding ROMs etc, is not unlike setting up your own Linux distro from scratch. It's powerful, but it's not a sleek or unified experience and the UIs are less than intuitive.
On the other end of the spectrum are things like the retro Atari VCS, or Analogue's line of FPGA-based emulator handhelds / consoles, or those "40 games in a joystick" type of things you see at Walgreens.
Apple could easily fund a bunch of those OSS emulator projects, and build a better version of RetroArch / MAME integrated into Arcade... and license games from the rightsholders to make it legit.
Thinking down the line, maybe with good Xcode integration, there'd be a good way to package new "retro" games for those platforms and sell them through Arcade or the App Store.