Keep in mind when Morrison wrote Animal Man and Doom Patrol he was not a big name, he was an unknown writer coming over form the UK who hadn't done anything in the US market. It was those books that started to make him a name in US comics. And it was the freedom to do whatever on those second and third tier books that is not available on the books featuring the big characters that really let creators establish themselves. With DC narrowing its line to the top tier characters, I am not sure you ill see books featuring D-list character or lower tier titles for that to happen anymore.
-M