"Just go! You're making us look bad!"
C'mon, if the map-thing didn't bring out the farcical and goofy part of Guybrush I don't know what did!
But I think you're right. Guybrush has grown up. In character-years I'd say at least half a decade if not a decade. In real terms, Dominic Armato must be about a decade older, the Emperors of MI are now two decades older than when Ron Gilbert went 'hey how about a young girl who wants to be a firewoman?' and so it's quite unavoidable that Guybrush will lose a certain element to his character. But I think this hasn't necessarily ruined him. He's still quite goofy, and while Morgan is a fan-girl, he's still a bit of a loser. It would be nice if one island hadn't actually heard of him, though. Like that no matter how hard he tries, how many times he literally saves the Caribbean, he never gets recognition as a proper pirate by everyone.
..Then again he's got that uber-cool hook now. Am I the only one contemplating unnecessary amputation?