It's not that regions are underdeveloped conceptually. But they certainly are in execution. For example, Saffron feels like the only town that really represents Kanto, while Ectruteak is really the only city that represents Johto. If you transplanted Cerulean City into Johto, there isn't really any way to tell the difference. And as far as city deisgn goes, the way even Gym towns, such as Mistralton, are still dinky, undeveloped backwaters, despite having the only airport in the entire region, continues to be pretty weird.
In the old games, yes, it didn't come across well. In the recent games, it's very easy to see what the locations convey. Sure they don't always have a lot of stuff there, since it is just a town in a big RPG after all, but you can sense the point behind the place.
I was actually confused by that. Why would you need an airport if you can just use a Pokemon with Fly? I understand they ship "cargo," but why couldn't Pokemon do that as well? If a Pidgey can carry a human, I imagine a fleet of larger flying Pokemon can carry some weight. Even if planes are needed, it could explain why having the lone regional airport doesn't necessarily make a place a thriving metropolis since most people never need to use a plane. It's like in Harry Potter, why use floo powder when you can warp?
They actually explain that, at least in B2/W2. Pokemon can't carry as much cargo as a plane, nor as fast as one. In B2/W2, they opened up the airport for passenger planes, since not everyone has access to a Pokemon that can fly.