In a world of declining general intelligence, not everybody is over-promoted with respect to intelligence.
Some people have the level of intelligence which would have been commensurate with their position in society about a hundred years ago.
Who are these people?
They are those of very high intelligence (by modern standards) but low conscientiousness and agreeableness (low empathizing).
In other words, they are intelligent people with awkward personalities that mean on the one hand they do not get promoted (because they have awkward personalities); while on the other hand they do not want promotion (because they know enough to recognize that that they are not capable of functioning properly at a higher level than they already are at. Not that others could do better - they cannot - but that they themselves could not do the job properly.).
Such not-over-promoted people actually understand what they are doing at the level at which they are doing it; and can provide a critique of what has happened and what has gone wrong.
I don't want to be too specific - but the handful of people I know who are potential geniuses (or unrecognized geniuses) are all functioning at lower levels than would have been commensurate with their abilities 100 years ago. (This is, I think, due to the trend for requring ever higher levels of docility, obedience and friendliness/ non-abrasiveness from employees of bureaucracies).
And I know of many more people of very high intelligence who are at the level where they would have been 100 years ago - but (becuase of the general delcine in g) are consequently of one-standard-deviation-plus higher in intelligence than their modern co-workers at the same level.
Also, I know of quite a few people of very high intelligence who are pretty much unemployable in modern conditions - however, perhaps that was always the case, perhaps there always were such people.