> it was being the only one in your city to be able to solve a complicated math problem, it was immortalizing yourself because you discovered a proof and added to the ever expanding human knowledge

I think if that is what one builds an ego on, being better in a discipline than most others, that is a good way to go into isolation and depression. With or without AI.

As Grant lays out in parts of his video, teaching, helping others, socializing etc. will always be valuable skills and much more likely to lead towards happiness.

And while I don't know how the specialized problem solving roles in a future with an actual capable AI will look like, I am sure it will continue to be a useful and needed skill as well. Without everyone having to take on a manager role.