Naturally we go through a period of believing everything we're told when we're kids, and transition to comparing everything we hear to what we've already heard before as we grow up.

(This is an inexact approximation, but in my more cynical moments it strikes me as only very slightly inexact.)

Don't underestimate the power of variations.

When shaping behavior in animals, we start with something the animal does naturally and differentially reward natural variations. Evolution of biological systems also involves differential selection of naturally occurring variations on existing systems. So it's certainly possible to get "something new" out of mere "variants of something [that already existed]".

That said, many cognitive systems do also seem capable of insight, which seems to be a completely different kind of process. Dennett and Schank here seem to be dismissing the very possibility of insight, though I assume they are doing so rhetorically.

Depends how great the variance is. Sounds better if you say that people benefit from having things they're learning related to familiar topics.

This does raise the question of how anyone learns anything in the first place.

Perhaps most people learn like this: They already have an idea X. Then they hear a very similar idea Y, so they accept it, although they interpret it as X. But once they agreed that Y is their idea, and they hear it repeatedly, they gradualy become aware of Y as something slightly different from X. Thus they made another inferential step.

Perhaps many people are willing to learn only when it does not feel like learning.