Why is Ayn Rand's Objectivism philosophy dismissed by academics?

This is a question in response to this other one that I asked. I didn't really get a satisfactory answer, mostly because it seems like Rand's work is largely ignored by academics. The highest voted answer starts with "you'll be hard-pressed to find a serious philosopher who takes Ayn Rand seriously". Why is this the case? To a layperson like myself, her ideas seem pretty well thought out, self consistent, and thought provoking, if a bit black-and-white. Is her work lacking rigor? Is the problem that her work takes the form of fiction rather than non-fiction? Are the ideas presented flawed in a way that is not obvious to me?