Apple laptops are known to come with hardware with very shitty open source driver support, there's not alot Canonical can do if they don't get good drivers for the various hardware components.
2) They could improve the other aspects of the experience that is crap on Apple hardware, like display connection/disconnection, sleep/wake, battery life adjustments, keyboard layouts, et c. It takes about a full day to make a mac not suck after installing Ubuntu.
Everything works fine on my MBP except that the desktop is a postage stamp and unusable on the retina display. I tried making things scale but different programs pick up different settings from different places and most look atrocious.
... and sometimes they have even better support than macOS. ;-)
E.g. the 2016 Apple MacBook Pro with TouchBar supports DisplayPort-daisy-chaining, while under macOS you can only daisy-chain monitors if they support Thunderbolt.
