What made the Ostrander/Yale Suicide Squad work and others not? John Ostrander and Kim Yale, along with Luke McDonnell, Geof Isherwood, Karl Kesel and other artists. They were creators who were absolutely at the top of their game over the course of Squad's 66-issue run, and you can't really get away from the fact that when Ostrander came back for stuff like Raise the Flag and the Blackest Night one-shot, those books were immediately right back in step with some of the best stories of the run. They were, hands down, one of the best creative teams in the history of superhero comics.
But at the same time, I don't think that's the whole story. When you get right down to it, Suicide Squad wasn't just a product of its time, it was the kind of comic that could only really happen in 1987.