But the thing is, much like Batman's skills, Luthor's genius has been overblown to such a level that I don't buy him as human anymore. He can come up, in five minutes, and completely effortlessly, to problems that have plagued humanity for thousands of years. No, I definitely don't buy him as a human. If he were in the Marvel Universe, he'd be a mutant with the mutant power of super-intelligence.
And even if I could buy him s a human? As you said, Luthor would need to be in charge for humanity to accomplish anything big. And, knowing him, he'd be pretty much totalitarian: even in the Red Son AU, where Luthor is a good guy and does end up leading humanity to greatness, he does everything on his own, single-handedly, refusing to let anybody (even his own wife) in on his plans. How could that push humanS to develop solutions? Humanity as a whole relies on him, just like it would otherwise rely on superheroes. In the far future of Red Son, after Luthor's death, people can't come up with a way to prevent their planet from exploding, and their whole race (but one baby) perishes in the explosion.
As for the possible underlying problem with the society, I don't believe that any police force, no matter how well-funded and organized, could prevent all assaults. That's the thing with humans: they have limits. Remove the limits, and you remove the humanity as well. It's no coincidence that the robot in The Bicentennial Man had to give up his immortal and artificially efficient body (particularly the brain) for humanity to finally accept him as their own. It's the reason that Batman, once a living glorification of human's potential, is now mocked as "Batgod" by his own fans because he can do anything.