I don't think the fault lies with Safety Management Systems but rather with management who fail to use the Safety Management System. They have all provided splendid SMS documents to the CAA and thereby obtained the tick in the box.
However, the next problems then frequently rear their heads. Eg. The SMS document sits in a bookshelf unused; the SMS uses high falluting language and concepts which are often a mystery; Managers fail to grasp and/or 'buy into' the philosophy of SMS; Safety Management Systems can be and often are overly bureaucratic; many of the CAA inspectors/regulators have never actually operated a SMS themselves etc etc.
The concept of having a 'system' for managing safety is excellent without question. Its introduction into the world of Airports has been haphazard [although not always]. As spitoon says, it is remarkable that even the AAIB make scant reference to SMS in most of their reports.
Helen49