I understand what you’re saying and I am aware that replacing distinct groups of people with broad political structures is a far from perfect approach. That could create an issue comparable to giving civ leaders in the Civilization series. Sooner or later you will end up with Alexander the Great or Cleopatra leading your civ in the modern era or starting with Roosevelt in antiquity.
I just think that the chronological order of progressing through the ages was never as strict or well defined in the Age of Empires series as for example in Civilization, let alone the scope difference.
For me, it has always been the same exact civ growing from weaker to stronger rather than evolving in a chronological manner. AoE hasn’t done that well in historical depictions to feel such a change. If they really decided to change this now… well we’ll see how it pans out and judge
Another possible solution would be to combine both cultural and political descriptions, similar to Crusader Kings III.
Or to design states and groups of people in a way that correspond to specific sub-parts of their history where all featured civs can at least roughly fall within the same timeframe and say that co-existed. Although, personally I would probably have no issue in seeing states that were at some point abolished while others kept on living for centuries, as long as they did even partially co-exist as major powers.
In any case, concessions have to be made from both sides and it’s up to the designers to find the golden ratio so as the civs to make the most sense and at the same time serve the needs of the game. Those rumors have only deteriorated my opinion on the matter but we’ll see. It may come out well or be a total mess.