I think it really gets down to how much great content a smart writer can come up with in a given amount of time. For the big broadcast shows, like Big Bang Theory, you have one or two chief writers and around a dozen staff writers all wracking their minds trying to come up with stuff for the show. When some staffer comes up with a good idea, the chief writer will do the final edit to maintain the characters' voices and attitudes, then they hope for the best. That's the typical comedy or average drama model, but imagine writing 23 very complicated murder mysteries in a single year... how can a show like CSI or SVU successfully write 23 fascinating and engaging mysteries a year?
I like the way the UK TV shows are produced, such as Doctor Who, Sherlock, Foyle's War, Endeavor, and so on produce shows - four to thirteen episodes in a given season, each one extremely well crafted and worthy of legendary status.
And, Haywood is right, AMC, FLIX, ScyFy and others have followed that same model very successfully. Some of the most memorable, addictive, and entertaining shows are those with fewer episodes. I mean, has anyone tried watching Elementary as a contrast to Sherlock? The characters in Elementary are very well crafted, but the stories get dumber and dumber and the Sherlock character seems to find the impossible to FAR too extremely unlikely levels as they run out of ideas.