Does pop cap still make sense?
Typically the reasoning pro pop cap are twofold:
Deathballs
Performance
Performance mostly is not an issue in this day and age, therefore let's focus on deathballs:
I have seen Pro players and us casuals complain about the same thing over and over again -> laveraging an advantage in the lategame and converting it into a victory is problematic which often times lead to slugfests in imperial with a constant back and forth and near unlimited resources. One of the reasons for it being the population cap blocking the player that is ahead to move even further ahead and finishing the game with an economic or military advantage.
Now, one could argue this is a comeback mechanic but I can hardly see the benefit of it as the pop cap introduces a lategame unit rebalancing in favor of the most pop efficient unit types (Knights, Elephants etc.) which in turn breaks the counter system as you cannot have 3to1 spear to knight ratio anymore etc. because you just lack the room for it. That is also why army compositions converge in imperial and imperial fighting feeling more static than in any other age.
The introduction of pop cap increase mechanics for FFA Nomad improved the mode a lot and made it avoid stalemates for the most part. I would like to see pop cap increases for other game modes as well. I think everyone would benefit from it.