Outside of physics, McKay is frequently quite a moron

So true. Which initially made for a really good character, because he was just a moron and thoughtless, not a moron and thoughtless to hide his inner pain or whatever. But by the end of season 5, it seemed like too much the latter, for me - maybe because I'd become coloured by fandom perceptions, I'm not sure, but it definitely seemed like Rodney had to be perfect by the end, and that had to be part of his perfection, not a nicely human flaw.