I think you have made a valid point guilt!
Look at how the place was thirty years ago and look at it now.
Having worked in what some may say was a relatively high position I agree that there are those national staff who were promotable.
There were also those (sadly they were in the majority) that didn't give a damn about putting in a fair day's work.
I had one national working for me (who was well connected) that took a year to produce what his expat colleague could produce in one week. Unfortunately and because of his connections, nothing could be done to remove this man.
The work ethic rarely appeared to be present.