3rd place in their CL group suggests otherwise.
I hardly think one season (the Club's first) in the CL is enough evidence to base that upon.
Besides Bayern and Napoli are no mugs, there is no arguments that they should escape the group but failing to do so doesn't make Mancini a shite tactician.
Naive perhaps, but he is a good manager and will continue to bring success to City, whether that be the ultimate prize of European football depends on a lot of things, Barcelona, managing the egos of the City squad, how long the Arab owners remain interested, and of course how they are managed.
Mancini may not be as tactically astute as Rafa, Pep, Mourinho, et al, but he isn't shite.