Not really?

If there's a range of "how aggressive a bear can be", and it's mostly driven by genetics, and aggression is heavily selected against in the environment? Then you can get a considerable reduction in aggression in the span of as little as a few generations. Bear generation time is what, 5 years? They coexisted with humans for a long time now.

Now, traits with weaker genetic components (i.e. if bear aggression is only 50% genetic) can take much longer. Even more so for traits with low variance, or highly complex traits and behaviors. But evolution isn't always slow. Certain changes can happen quickly - about as quickly as you can apply the selection pressure.