When I visited the UK years ago, I realized that the BBC produces a great deal of really crap tv shows. But, otoh, I also noted they did some very good educational tv programs, and there were also very good dramas.
We get "the cream of the cream" of British tv over here. Even old British tv can be very good.
Awhile ago I re-watched an old late 1950s British show, "QUATERMASS AND THE PIT." It was a six part series in b&w on DVD and it was well made, well acted, and intriging. In 1966 a color movie was made from the screenplay called "FIVE MILLION YEARS TO EARTH." Some people here may have seen it as it's been on American tv for decades. It's the same basic screenplay, made with a little higher production values, but, still true to the original story line.
There have been a number of other very well done British shows on American tv. They CAN do it, they're a smart people.