Some episodes of Sherlock are great and others are fucking appalling. Sherlock should be simple. A mystery happens, seemingly impossible events take place or else deduction seems impossible but clues are found along the way which only Sherlock (and occasionally, the more switched on viewer) takes notice of. At the end of each show, the mystery is revealed and the solution should make perfect sense in hindsight, ideally such that it could be solved by the viewer, albeit that this should not be easy.
A meta-narrative, stretching across the series is acceptable as long as follows those same rules. Characterisations, acting and style are all important but secondary to plot, which is the star of the show. There are enough mysteries in the source material to adapt so this should be possible, even if the writers find Doyle a tough act to follow.
Sometimes we get that with Sherlock and that's when the show works. But often the mystery is resolved by way of deus ex machina or is marginalised (or in some cases, is not even present) by a more prosaic action-adventure main plot pitched somewhere around Dr Who with some James Bond thrown in.
Dr Who, which involves many of the same people, has similar problems with the MacGuffin (the fact that the Doctor can go anywhere in time or space to find adventures) frequently mistaken for the actual purpose of the show.
However, when Sherlock works it works very well. The Guy Ritchie films (or at least the first one which I have seen) are not really anything to do with Holmes on anything but a purely superficial level.