If you were to say 20 year old game, then maybe. But there has been no humongous changes in the last three years to warrant expecting civ V to be so incredibly revolutionary compared to civ IV or BTS.
I'm sure they didn't forget, it's just that even if those ideas made sense for civ IV, they're still back to the drawing board (literally) with civ V and you kinda answered yourself there: 5 years of continual patches is 5 years. Come back in five years and then compare the game.
So you're saying that they forgot the 3-4 years of development plus 5 years of continual patches worth of experience when developing CiV?
I'm sure they didn't forget, it's just that even if those ideas made sense for civ IV, they're still back to the drawing board (literally) with civ V and you kinda answered yourself there: 5 years of continual patches is 5 years. Come back in five years and then compare the game.