Re: "the system has a more modern and 'flatter' look"
The UI, on any operating system, is something people are reluctant to change. We still have, with slight differences elements that have been here since Windows on MS-DOS. Look at how minimise/maximise/close has and hasn't changed.
I have seen ideas for UI changes which might be improvements, but the struggle to overcome all those decades of habit made them more like failures.