I guess when it is all said and done, it comes down to assessment of individuals against their peers. The best guys will suceed whereas the chaps that don't measure up get the short end of the stick.
These are fairly harsh words and a new and bitter experience for a younger generation, many of whom have been the victims of education systems that are prohibited from grading them due to perceived problems of self esteem etc.
However the demands of airline aviation are that on each flight the destiny of some 400 lives, $200 million of airframe and $1 billion of insurance payout are in the balance (and possibly the commercial survival of that airline). This sort of responsibility doesn't allow for automatic promotion of mummy's little boy who is used to been molly-coddled and spoonfed.
To survive in an aviation career, you need to take full responsibility for yourself. Any flight crew-member with a modicum of commonsense will devote their energy to finding out what is required for promotion and prepare and present themselves in the best light.
OTHR, any crew-member who goes around trying to find someone else or some other system deficiencies to blame for their own inadequacies to be upgraded, will be doomed to failure. No one respects a person with a lack of self-disciline, and more importantly, no one trusts such a person.
From the time you put your first foot in the door at CX as the most lowly S/O trainee, you are being assessed for Command (do not take these words lightly).
As I mentioned earlier, do yourself a favour and make a decision now to check out early, or do everyone else a favour and check out early.
If you let yourself or anyone else screw up your progress to Command, it's your fault, period.