What's interesting is that in re-reading the earlier books as I have been, Ron's really not like that. He's a little snarky and dim at times, but no more so than the others can be. (Hermione's academically smart, but quite clueless and insensitive at times when it comes to interacting with other people.) In fact, he's even the voice of reason a lot of the time, very much the strategist, and even his seemingly insensitive moments are occasionally this if looked at a certain way.* It seems to be later that we started seeing doofy!Ron. I do think his insecurities played some part - you mention Neville, and I wonder if Ron didn't have the reverse problem; Neville never felt overly talented, which made him incredibly clumsy and insecure and forgetful, but Ron was fairly confident until he realized he'd befriended a famous wizard and a child prodigy. He and Harry fight over it in GoF, but I don't think it ever really went away. However, I would have liked to have seen a more self-assured and mature Ron in the epilogue, because a lot of DH seemed to be Ron coming into his own.

*For instance, when Buckbeak "attacks" Draco in PoA, Hermione's worried about Draco, and Ron's like "forget Malfoy, I'm worried about Hagrid." It seems like Ron just being dismissive because he doesn't like Draco, but I think Ron had already worked out that Draco was going to use this to make Hagrid's life hell. And while he could've been more supportive of SPEW, he also recognized that Hermione's methods were awful. So while at times his empathy seems lacking, I do think he was trying to keep everyone grounded and focused in the long run. A chessmaster if there ever were one.