I think perfect competition is impossible.
It is an ideal to be approached asymptotically, and a correct goal for consumer-protection regulation. Consider for example antitrust law, truth-in-advertising laws, product safety standards, etc. and how they directly match up with and promote those conditions.
It's just not a system that is sustainable. The incentives are simply wrong and the society built around those incentives can't maintain a system of perfect conditions even if one were to exist.
It's not a system that is sustainable in a liassez-faire libertarian Hellscape, because of course capitalism left unchecked devolves into cartels. But it is a system that can be maintained with appropriate regulation.