The British Empire, like all the European empires, was created by desperadoes and ambitious, frustrated peasants. Not by persons of privilege.
Not - ‘built on the lies of privileged white men’.
The best parable of truth of colonialism was, of course, written by Kipling. “The Man Who Would Be King” lays it out.
This is the epitome of cultural appropriation.
But they were acting in the name of a king or queen, and their conquests wouldn't have lasted without Britain to back them up. After all, what happened to Kipling's hero?
America, Canada, and Australia certainly were built up by ambitious peasants, but the British Empire in Africa was largely created by the army and by diplomats, and even in the New World, land grantees and wealthy sugar and tobacco planters did a lot to make the empire profitable.
But of course, 19th century convicts weren't up on 21st century CRT talk. It's likely that Magwich hated the rich, and just possible (though unlikely) that he might have had some sympathy for the aborigines, but he would have seen that it was people like himself who were the chief beneficiaries of the settlement of Australia.