They each have different aims with their writing. Gladwell wants to illustrate things as they are. Rand wants to illustrate things as they could be.

Gladwell's writings undermine Rand's beliefs justifying her vision of what could/should be.

To some extent, yes. As I said: Gladwell is like a Rand villain. But they aren't polar opposites. I doubt Rand ever saw the world as stylized as she wrote it. She's openly a Romantic Realist.

Gladwell opposes Rand. But they still hold fast in certain things. The opposite of Rand is not the person who says that people aren't responsible for their success. It's the person who says that civilization isn't a success, that human beings are beasts, that the solution to our problems is to go back to being savages. Similarly: I think Rand would disagree with Gladwell's claim that nobody is responsible for their life, but she wouldn't dispute his findings. She would just argue that they aren't as relevant as Gladwell thinks they are.