The other problem that Windows and Linux have, but Apple doesn't, is that the DPI control is *global*. I have a nice 150ppi laptop screen, and things look great if I set the scaling appropriately on it. I also plug it into a nice big 96ppi monitor, and things look great on it if I set scaling back to "normal". But then things are tiny on the laptop display sitting right next to it.
Apple avoids this by only ever doing 2-to-1 scaling, and doing it on a per-display basis.
I've seen a few people argue against true resolution-independence on the basis that the current mechanism does something vaguely sensible on the monitor vs. TV use case where naive resolution-independence wouldn't. There seem to be two different variables that get conflated a lot: the actual density of the display, and the desired physical font size, which depends on the user's viewing distance, eyesight, personal preference, and even the PPI (I can read smaller fonts on higher density displays).
There's also the issue of how non-text UI elements should be scaled. For instance, widget borders would probably look pretty terrible at non-integer thicknesses. On the other hand, on a 300+ PPI display, single pixel borders start to be pretty hard to see.