Mythicized past? One of the lesser things the English did the Scots was to ban the Kilt, and that happened after Scotland was in the UK. Robert the Bruce did lead the first war for Scottish Independence.
Robert de Brus was an Anglo-Norman aristocrat, with lands on both side of the border, who cared mostly about his own personal power, not some proto-nationalist "Scottish independence" a la Braveheart. William Wallace conducted some of the most brutal raids on English civilians. These were not "good" people simply because they fought against a bunch of other equally violent noblemen.
Also the Dress Act was very much in the aftermath of a Jacobite Army invading England who also encouraging a French invasion of England and very nearly succeeded. It was hardly the most significant thing that happened in the highlands after that either, even though any regime would have to take some steps to prevent future rebellion, Cumberland's "pacification" of the highlands was considered excessive even by the standards of the day.
Also, if we are going to engage in rampant presentism whereby we try to anachronistically fit the past into our modern prejudices, we can say Bonnie Prince Charlie, as a believer in Divine Right wanted to roll back the democratic reforms and so was a "baddie". That's how it works, isn't it?
Border disputes between Northumbria and Scots over a thousand years ago or Catholics vs Protestants 30 years ago, there's nothing mythical about the claim England has **** on the Briton and Irish Celts for so long they were doing it before it was even formally known as Angleland. And the prejudice continued for a very long time.
This is exactly the kind of mythology that takes some modern political entities and reifies them in the past.
"England" was oppressing "Scotland" before either actually existed?
Much of what is now Lowland and Border Scotland was part of Northumbria, or Strathclyde or some other Kingdom that wasn't "Scotland". "Scotland" was really several different cultures that were eventually united by conquest and later on became Scotland. Your beloved "Celts" (a modern myth, not a meaningful historical people) violently eradicated Brittonic culture from Scotland, not the English. The "Celts" were imperialists and colonisers too.
The idea that everything that is now Scotland has some intrinsic "Scottishness" that has existed since time immemorial is entirely mythical. It was a product of conquest and violence, a bit like England.
Both "Ireland" and "Scotland" have long traditions of raiding, thieving, raping, and slaving in England, but this tends to be overlooked in favour of some fanciful notion that they were a brave band of freedom loving warrior-poets who desired peace but were unfairly oppressed. It was a load of violent rich folk fighting over who had the biggest ****.
All sides were brutal, engaged in atrocities and saw violence as a legitimate tool for expanding power both internally and externally. All sides were a serious threat to each other too. So they fought, because that's what people did in such circumstances.
England was invaded by Normans. Ireland was invaded by Anglo-Normans. Scotland was ruled by Anglo-Normans, after "Celts" had conquered non-"Celtic" people. The North of England suffered the worst of it, yet for some reason this is all "England" oppressing the "Britons and Celts".
That people were neatly divided into "goodies" and "baddies" whose politics align with our modern fancies, especially those of the American diaspora, is very much mythical.
Braveheart and Bonnie Prince Charlie kitsch shortbread box nationalism is not a modern and progressive force any more than Little Englander nationalism is.