I think TV shows and films remind you more of the time they were made than the time they were set. Bonnie and Clyde is very 1970s, High Noon is very 1950s and so on. Downton Abbey is very 2010. It's Daily Mail 2010. Daily Mail readers aren't monsters - though we pretend they are sometimes (I do anyway). They are aware, perhaps in an unexamined way, of bad things which happen in our society, but they desperately want them to be addressed without challenging established power structures. Sometimes that makes them cruel.
In Downton Abbey there's a similar uneasiness about oppression, but (as in some wet dream of a Mail reader) oppression is comfortingly addressed item by item, by the beneficence of those above, condescending to those below. I feel it's Valium for the modern worried, who need to feel that the ruling classes have it all in hand.
Also, there was a letter in the Guardian today noting that religion was entirely absent from the series. No worship, no senior clergy, no piety. This is not a series in any way about our past, it's about massaging the anxieties of the present.
People have said they saw double yellow lines on the road, and telephone wires. I didn't notice them, but I often miss stuff like that. That kind of thing doesn't bother me.