Re the settling of high-time 732's to Nigeria & the like -
I'm not sure of the price of jet fuel there, but I bet it's pretty cheap. Thus the incentive to acquire & operate newer jets (less fuel burn, but high upfront cost) is pretty low. Couple this with penny-pinching maintenance, and the outcome is predictable.
But a well-maintained, upgraded 732 would be a fine bird to fly - just a wee thirsty though. It was built to see many cycles.