It's not that deep. It's obvious that AoE marketed itself as an RTS game and not some kind of 4X game with complex diplomacy/subjugation mechanics. Competitive RTS games are at their best when each faction maintains some unique characteristics (as opposed to assimilating opposing faction tech), otherwise, you lose balance and/or strategy. At the end of the day, good gameplay should be prioritized over flavor.

ETA: To add, as a young nerd I did appreciate the history section of the game.