Drug companies are able to pay PBMs — as well as hospitals and some doctors — to make sure cheaper drugs are left out. It’s as simple as that. Drug companies pay everyone along the way so that lower-price drugs lose.
You don’t have competition when the system is gamed, and those who argue against “single payer” health insurance always hinge their argument on competition. If you don’t want to change health insurance then do something about the costs with regulation that forces competition.