Well, I really don't agree to that. Sure the story may appear sometime repetitive, but I find that the author manage to make the reader thrive with the destiny of the bizantine empire, to see the hordes grow and grow more powerful. Even if the byzantines win a lot of war, each defeat can be the beginning of the end. Look at the lost great holy war for Bulgaria... Who knows what will happen ?
In terme of stylistic approach, the author manage to create a nice background of religious intolerance, neverending state of war world, and make the byzantine nobility looks like crabs in a basket, waiting for an opportunity to strike the emperor. The later is almost always cruel and deceitful, which is reflected by the difference between a plot success screen, and the "official" story about the plot. It is a very cynical approach. How many time have we seen a princess of the byzantine empire puppeted as a claimant to the throne killed by the player, when the story tells that hated Aztec did the work ? For me, it is brilliant and definitively the style of the author.
Yet, being like "meh, people did better things before" is weird... Shall that mean that each masterpiece is the end of history? Look at the lord of the rings? It is certainly, for me, one of the major fantasy novel, if not the greatest (personal opinion). Yet I won't tell other fantasy authors something like "why are you bothering writing ? Everything has been done already.". I haven't read the AAR you are pointing, but I will give a look. Anyway, whatever the quality of the AAR will be, I know I won't stop reading and following this one.