I’ll check it out. But this seems to approach accessibility as a feature to be turned on or off. Most of what it enables, based on Apple docs, is not just enabled in Windows and many Linux window managers I’ve used, but it’s something that developers actively utilize.

That's not where macOS came from. For Windows and Linux, "in the beginning was the command line" but not for Macs.

There's plenty one can do in macOS and its native applications with a keyboard by default, those that need more can enable "Use keyboard navigation to move focus between controls." Those that need even more enable Full Keyboard Access. These settings aren't on be default because Apple has decided they'd just get in the way and/or confuse people who use the keyboard but rely on it less.

In Safari specifically, by default pressing Tab doesn't focus links as it does in every other browser because most people use a cursor to activate links, not the keyboard. There also tend to be a lot more links than what Tab does focus, form inputs.

Macs try to have just enough accessibility features enabled by default that anyone who needs more can get to the setting to turn it on. Something I just learned Macs have that other OS/hardware doesn't is audible feedback for the blind to login when a Mac is turned on while full disk encryption is enabled.

I'm not claiming Apple gets everything right or that their approach is the best, I'm just trying to describe the basics of what's there and the outlook driving the choices.