if you ask them to do any planning, for instance, they'll come up with designs that sound good but fail: they parrot back other people's plans with minimal modifications

Guessing the teacher's password describes a common human behavior. An AI that behaves the same way not just passes the Turing test, it might really be said to be as intelligent as a relatively stupid human.

Also, there's a huge quantitative difference between a student repeating what the teacher said, and an AI repeating at will everything written in all digitized books and Internet sites it has read. An AI that is a little less intelligent than a human in some areas will still be vastly more intelligent than any human in most other areas. Even if humans remain much better at certain tasks, it may not truly matter.