The problem isn't that he has a lack if talent , it's that Carlsen has a massive edge over the most talented players in the world. In addition Nakamura struggles with Carlsen more than most around his level.
I could give loads of examples in which players have had edges, sometimes for years at a time before they come around to their style. And trust me, it happens.
Even if he does, the underestimation of his abilities are really overlooked here. I don't know if it is because some people consider him a ''punk''... but as far as I am concerned, anyone who can't see him being his rival obviously can't see talent when they see it.
Nakamura is A rival, is just that he is not THE rival.