Thinking developed naturally as a tool that helps our species to stay dominant on the planet, at least on land. (Not by biomass but by the ability to control.)

If outsourcing thought is beneficial, those who practice it will thrive; if not, they will eventually cease to practice it, one way or another.

Thought, as any other tool, is useful when it solves more problems than it creates. For instance, an ability to move very fast may be beneficial if it gets you where you want to be, and detrimental, if it misses the destination often enough, and badly enough. Similarly, if outsourced intellectual activities miss the mark often enough, and badly enough, the increased speed is not very helpful.

I suspect that the best results would be achieved by outsourcing relatively small intellectual acts in a way that guarantees very rare, very small errors. That is, AI will become useful when AI becomes dependable, comparable to our other tools.