My guess is that those on the ideological extremes - be they libertarians, for whom the individual trumps community and economic freedom trumps prescribed relationships, or extreme progressives, for whom the individual also trumps community and for whom personal lifestyle freedom trumps prescribed relationships - will equally find Downton difficult to take.
For all its aristocratic nostalgia,Downton does admit an appreciation for other, more modern values. In an important conversation in season 3, Matthew tells Mary that he realizes that Lord Grantham views Matthew's concern to make the estate operate successfully as "middle class," but adds that "the middle classes have their virtues too, and one of them is husbandry." On the other hand, it is Robert's role to remind his modernizing daughter and sons-in-law that relationships matter along with money. Thus, the very revealing recent episode in the current season when he lends money to the son of a recently deceased tenant farmer so he can pay off his father's debt and assume the tenancy himself (even though it would be more modern and efficient for the estate to foreclose). What decided it for Lord Grantham was the young tenant's reminder that his family had been farming the land for generations "in partnership" with the Crawleys.