DA was supposed to be an improvement on USDS by somebody who really knew that world (sort of), and in the beginning it was.
Then they started to get sensationalistic, killing off characters to spike the ratings, but I don't think it was worse than USDS in the 70s -- and it was better than the recent version.
I don't remember the American series. I heard it was awful. But the audience for high society period costume drama is so much smaller in the US that it couldn't possibly have been a success on American commercial television.
DA stunk on ice, was inacurate, in many instances, kept looping the same damned story lines, and never resolved most of them, until the very last show; a CHRISTMAS SPECIAL at that! And yes, I watched all of it; every single show.
PBS sliced and diced and cut out lots of scenes from the original Brit shows. It didn't matter all THAT much, but just so you know.
Fellows pretends to know all about the aristocracy and really isn't "one of them" at all; mostly, he just knows some now...since he has been knighted.
OTOH, the two great authoresses, of US/DS, came from families whose parents/grandparents/or their family members had been servants in great houses and knew those family stories. And both Marsh and Atkins are far better writers than Fellows can even begin to dream of being close to!
I have seen UP/DS long after the first run and HELL YES, it holds up and does so very well!
You can blame some of the deaths, of leads, in DA, on the siren call of Hollyweird, where some fled too and died. No, not literally...figuratively; re their being seen and/or lauded.
DA was shown WITH COMMERCIAL BREAKS, on Brit T.V. and the Brits has hissy fits for two reasons: 1) far too many commercials 2) most of the actors mumbled.