alt Hacker NewsSpeaking for AOE2, the most popular AOE version,
It's not a great argument because the game takes place pre-empire, and the end of the game is intended to be when one player, the winner, is now an empire. This is evidenced by the final age in the game being called the Imperial Age. Most empires in history fought their neighbors in more or less the same manner as exhibited in the game before they became big and strong enough to be an actual empire.
I guess you could make an argument that the game doesn't transition into the most powerful player beginning to behave like an empire in the imperial age as you keep steamrolling your opponents until the end of the game, but it's a weaker argument and it's not clear why you would want to change the entire game's mechanics right before the game ends.
Am I misremembering things? I played a lot of AOE2 in college and in multiplayer games one of my gotos was to attack someone quickly and force them into an alliance where they sent me resources, and then continued to demand resources so they could never grow big enough to remove the alliance and attack, then coordinate through them to attack other people. Seemed like a pretty good approximation of empires to me at the time.