COULD be a bit of a trigger shape/ geometry issue. What I mean is, on the fine end of things, there can be a difference in performance for an individual with a particular trigger shape or design/ feel/ pull weight....that doesn't occur with another very similar design.
Case in point: my little teeny Kahr CM9. Best trigger feel (to me) of any I've ever tried - though it is long. Many hate the Kahr trigger- but I shoot that little pistol better than ANY other. I have NO difficulty keeping the front sight dead on the target. The trigger has a total pull length of 19mm (including takeup) ....and a rated pull wt. of about 6.5 lbs. Contrast this with my Sig P250. A very similar trigger feel, also very smooth....but about 25mm total pull length and about 5.5 lbs. I shoot the 250 well, but NOT as well as the Kahr.
The Kahr trigger shape "fits" my finger perfectly. Totally comfortable, throughout the pull motion.
The Sig trigger, on the other hand, has an odd sort of angle at the very tip and just doesn't feel quite as comfortable, to me. The shape of the trigger is more rounded, on the front face, than the Kahr, so it "feels" less secure, even though both triggers are almost exactly the same width (approx. 9.5 mm). The Kahr trigger is flatter on the front face, which feels better (to MY finger).
The Sig, on the other hand, has a grip that is MUCH better in overall form (for MY hand), than the Kahr.
As another example, I can't get used to the feel of the Glock trigger at all (can't stand the feel of the trigger latch)....so I don't shoot Glocks well.
--------------------------------------------------------------------------
However, having said all of that, it IS possible that you just haven't put in enough practice with the M&P.
It certainly appears, from the results of others, as if there is nothing inherently "wrong" with the M&P trigger. I have tried them and the trigger felt good to me. But, maybe the M&P is just not quite YOUR "cup of tea".
Ultimately, ONLY YOU can decide.