Personally I agree with you Hoplite7, that in M2TW there seems to be a lack of diversity, however I have to agree with everyone else and CA, because it is Historical the way it is.

This is a later period, where most cultures already have had much contact and warfare with eachother, what worked and what did not work had already passed the evaluation perriod, and lessons had been learned in terms of warfare from the previous era.

So in a way what you feel is normal here, you went from the Ancient Period to the Dark Ages Medieval period. The only question to find out is which one you prefer better, which is personal to each player and style.

Yet eventually as moding devellops for M2TW more variety can be added.