Earlier quoted context omitted.
I think you're confusing dialect with language here. Scots and Scottish English are distinct from one another. The latter does borrow some from the former which leads to confusion. Scots is a language, historically equivalent and closely related to English but still distinct. It's a stretch to argue that "many modern English speakers derive from Scots root". At this point in history, most Scots speak Scottish English…
Hey, parent poster here, also living in and around Aberdeen for most of my life :) You're bang on about Doric being difficult for people from elsewhere in Scotland; I have family from the central belt and they really struggle to understand some folk up here!
https://www.youtube.com/watch?v=0isMWmwfO34
and Aye Can's Doric page [2] is part an audio map of Scottish Dialect
[2] http://www.ayecan.com/listen_to_scots/north_east.html
Sheena's Granny's Doric [3] has a flavour of the musicality of Scots.
[3] http://media.scotslanguage.com/library/audio/ayecan/census_n...
The Scots sort of sang their words, especially the Gaelic speakers, Orcadians and Shetlandic.
https://www.youtube.com/watch?v=v37bgydws0E
The BBC's postwar campaign to establish Recieved Pronunciation made the UK largely comprehensible to each other but at great cost to it's unrecorded linguistic diversity - at the time sadly considered vulgar.
Lang may yer Lum Reek ! ( Long may your chimney's smoke - a Fifer greeting )
Dinnae fasch yersel. - Edinburgh's Don't worry yourself ( Keep Calm )