Well, I have on more than one occasion for precisely this reason...
Sherlock, Last Tango in Halifax, Luther...
Or looking further back, Agatha Christie's Poirot, Prime Suspect, Absolutely Fabulous...
I really don't want to add fuel to other people's fires here (as you do have a point), but I just need to add some opinions to some of the examples you gave. .
Its kinda apples and oranges with a few of those examples. British TV shows will often reappear years after the last series wrapped up (after a consistantly timed run of series).
Consider the orginal AbFab's first 3 series were 1992-1995 (with fairly consistant timeframes between airings- all 3 series where shown around the winter block) before being wrapped up with no plans for more after the Telemovie in 1996. Jennifer Saunders just ended up being struck with the inspiration bug after the MirrorBall pilot to produce series 4 & 5 some 6 years later. This is more akin to the 15 years between Doctor Who then the 2 years between series of Who we're getting now.
Prime Suspect was regular and consistent in production from 1991-5 until Helen Mirren quit and it took 7 years to woo her back. This one is more so working around a famous lead. I'd put Sherlock and Luther there. Both those series got more inconsistent as their leads fame started to skyrocket.
Yes Doctor Who does have some complications when actors want to commit to other projects, but not to the level of when a series is built around one person like Helen Mirren, Benedict Cumberbach or Idris Elba when they started to make a name for themselves on both sides of the pond (not to mention regenerating has always been that get-out-of-jail-free card)
The Poirot was still 13 series over 14 years. Still pretty good. And they're number of episodes dropped towards the end as they had the issue of only having so much source material to adapt (same thing happened with Joan Hickson's Mrs Marple - thus why it ended with four Christmas specials over four years)
Certainly Who has its own unique set of conditions (Often relating to costs on what is a niche show) but we are now getting less over a longer period of time now, with little explanation as to why (its not like Jodie is filming a new series of
Broadchurch in the off time) and the show doesn't have the issues a lot of the other shows mentioned have (sole writers for the entire series, working around stars movie careers, limited source material)