We have multiple parts of the brain that interact in vastly different ways! Your cerebellum won't be running the role of the pons.
Most parts of the brain cannot take over for others. Self-healing is the exception, not the rule. Yes, we have a degree of neuroplasticity, but there are many limits.
Only if that was a singular system, however, it is not. [0]
For example... The nerve cells in your gut may speak to the brain, and interact with it in complex ways we are only just beginning to understand, but they are separate systems that both have control over the nervous system, and other systems. [1]
General Intelligence, the psychological theory, and General Modelling, whilst sharing words, share little else.
But what's driving a car? A generalist human brain that has been trained for ~30 hours to drive a car.