Excellent article. Two important quotes:
"Because the truth is that Doctor Who isn’t really like any other show on television when it comes to production. Excluding two-part stories, every single episode requires a new guest cast, new costumes, new props, new filming locations and – barring any use of the TARDIS – entirely new sets, essentially rebooting the entire thing every week.
When I spoke to Chris Chibnall late last year he revealed that he hadn’t had a single week off since taking over the series, only managing some time away shortly before our interview. Presumably the story was similar for other members of the production team, while the cast – Jodie Whittaker, Mandip Gill, Tosin Cole and Bradley Walsh – were back beginning a second 10-month shoot just a couple of weeks after the 2019’s New Year’s special aired on BBC One."
When I spoke to Chris Chibnall late last year he revealed that he hadn’t had a single week off since taking over the series, only managing some time away shortly before our interview. Presumably the story was similar for other members of the production team, while the cast – Jodie Whittaker, Mandip Gill, Tosin Cole and Bradley Walsh – were back beginning a second 10-month shoot just a couple of weeks after the 2019’s New Year’s special aired on BBC One."
"But this output was a one-off. In Davies’ co-written book (with Benjamin Cook) The Writer’s Tale he describes the stress and pressure he was under working at this rate while also overseeing spin-offs Torchwood and The Sarah Jane Adventures, and his successor Steven Moffat ended up splitting the sixth and seventh series into two parts to help manage the workload, returning for a full 2014 series before taking Who off air entirely in 2016 (save a Christmas special).
When you think about it, the golden age of annual, 14-episode Doctor Who hasn’t really existed for over a decade, so it’s not entirely fair to hold the Whittaker/Chibnall era to that same standard. Arguably in large parts thanks to the Who revival, sci-fi TV has also developed massively over the last decade and a half, to the extent that it possibly does take a little longer to build sets, craft props and create CGI to a screen-worthy standard than it did in the Noughties. Would we really want to rush and get an inferior product just to satisfy our own impatience?"
When you think about it, the golden age of annual, 14-episode Doctor Who hasn’t really existed for over a decade, so it’s not entirely fair to hold the Whittaker/Chibnall era to that same standard. Arguably in large parts thanks to the Who revival, sci-fi TV has also developed massively over the last decade and a half, to the extent that it possibly does take a little longer to build sets, craft props and create CGI to a screen-worthy standard than it did in the Noughties. Would we really want to rush and get an inferior product just to satisfy our own impatience?"
). And now technology has improved so CGI stuff should be easier. It's not like they have to re-render the TARDIS going thru the time vortex for each episode. 
such episodes would still need guest cast/director etc. Though they could be clever about this. Look at Eccleston's series. Three two parters means shared sets/cast, and one of those two parters could almost be considered a three parter given they featured the same set as The Long Game.
