You probably mean T1, as the repo covers MacBook Pros and not the iMac Pro. While I agree that hardware support isn't where it should, it's getting better. Hey, we even have a working driver for the internal keyboard since several months. ;)
No, seriously: Currently most effort is going into mainlining Bluetooth support for the current MacBook Pros (I expected that to land in Linux 4.17, although it still might get squeezed into 4.16) and preparing the keyboard/touchpad driver for mainlining as well.
The Wifi issue is really a shame, but as far as we know it's entirely to blame on Broadcom as their Linux firmware has an issue preventing it to work properly [1], something which can't be fixed by somebody outside of Broadcom.
And to be clear: That so much stuff isn't working under Linux with the current MacBook Pros isn't really something to blame Apple for. What Apple simply did is what they always do: Rethink how they can improve stuff and they did a great job with it. E.g. it makes perfect sense to connect the internal keyboard via SPI instead of via USB, simply for power-saving (and probably complexity) reasons. As Apple is the first vendor to do such things there are simply no Linux drivers for it yet. Or look at Bluetooth, which is now connected via UART. It appears that this will be the way to go for all vendors in future, but only a few are already doing it, so there are still some rough edges which need to be smoothed out.
https://github.com/Dunedan/mbp-2016-linux (T1) not working: audio, suspend/hibernation. 2/6 models working: WiFi
I'm probably most interested in hearing more about OpenBSD support, I'm not finding much recent info.