Greenscreening in Season 5

Like I imagine a lot of people these days after the release of the movie, I am rewatching the entire series. One problem I have with the show that I observed in my first viewing is the visually ugly look of using what I assume are green screen shots in many of the interior scenes in Season 5. These are almost always used in "upstairs" scenes, never "downstairs". I assume having the actors on a green screen cuts down on the amount of time spent shooting at Highclere Castle for many of the scenes taking place, for instance, in the Great Hall or the large library. The backgrounds are out of focus behind the actors (which makes sense) but something about it looks "off", static, and mechanical. The first time I started seeing green screen techniques being used in a series in a way that was noticeable was in the Netflix-produced seasons of Arrested Development. It looks obvious and makes one feel like cost-cutting measures are being used. Does anyone know more about the usage of green screens in Downton's final season? It may be fitting to say I didn't observe the fakery of green screens once in the movie version.