If you take a population of humans, put them on an island, and only allow those that grow tall to breed, after 20 generations you will notice a huge difference in the average height of your population.
You might already be aware of this, but it is important not to confuse the slow mutation rate, with a slow response to selection pressure.
Nor is it appropriate to generalise that because the modern day selection pressures are mild, humans somehow evolve 'intrinsically' slowly.
The 'cars' are evolving fast, because those with a low fitness are ruthlessly culled. Human populations can change fast when comparably strong selection pressure is applied.
