Usually when people complain about DNS, they're talking about stability issues. In this case I think he's pointing out how centralized it is, and how a bad actor could cause significant issues

At a local level, the most common issue I know of is ISPs blocking sites at the DNS level by feeding in fake information that redirects you to one of the ISP's blocked/parked domains. Usually implemented to prevent customers going to piracy sites. It's not much of an issue to subvert currently, as you can simply use any public DNS provider

That being said, much of that has been consolidated into a dozen or so tech companies. In the current political climate, I could see a coordinated effort happening between those tech companies to block sites deemed non gratis. Obviously there's still ways to subvert it, but the vast majority of user's won't be able to