The reason why I used a planet as the example in the analogy is because the supermassive black holes at the centers of galaxies tend to be, at most, a few percent of the galaxies' mass. The Sun, on the other hand, contains nearly all of the mass of our solar system. So a quasar is much more like Jupiter in the analogy: significant impact on the structure of the solar system (e.g. by preventing the planet that tried to form in the asteroid belt from actually forming), but a small fraction of the total mass, and in no sense the cause of the solar system forming in the first place.
Quasars are what happens when the nuclei of galaxies gobble up matter. This happens when galaxies first form, and can also happen when galaxies collide.