Age of empire 4 needs replay able single player / co op content. co op vs ai doesn’t count
The standard missions are like a book you play it once then never again.
Most of the strategy, rts, 4x, total war games above aoe4 on steam have more people playing cause they have better replay value with single player.
It needs a conquer map thats not fully story based, where you could play vs a friend or ai
Or story based campaign that you can pick your own path and its different every time you play.