Well in their defense, what can they really do? There isnt that much left. Yeah you can argue you can go further back before Rome got powerful but then most units were roughly the same and it was for the most part fighting in between city states, if my memory serves. Rome seems the logical step forwards. Afterwards they can try something new and daring.
This.

RTW2 is a logical step, IMHO, and one that will be met with great enthusiasm, I'm sure. RTW was probably the most popular venue of all the TW series, and it's the only one not to get a make-over. Hopefully they do a credible job with it.