AOE3’s richness and depth is both a blessing and a curse. It becomes more and more problematic that as the game grows the tutorials and sp contents did not catch up. Ironically in the whole series, this game has by far the deepest mechanics but also the shallowest campaigns with very out of date contents.
I always think more freedom and wider options is good, but that should be paired with good guidance in the form of sp missions, and that’s something AOE3 has not done well since 2005. You had 8 civs with vastly different playstyles and you can only learn how to play 3 reduced versions of them in the campaigns. I doubt anyone would figure out how to properly manage banks or Ottoman free villagers by themselves after finishing the campaigns.
As the game grows into 20+ very asymmetric civs, at least each civ should be given a set of small missions that teaches their basic mechanics and builds, like masteries in AOE4 (whose campaigns are also quite lackluster though). AOE2 campaigns function like this as well and there are already too many compared to the much more similar civ designs and simpler mechanics, in a good way. AOM only has three civ groups and each receive long campaigns that carefully guide you through every aspect and it even has introductory videos during the playthrough. AOE3 has none of them.
Because sp has little to offer, players either leave after finishing the campaigns (which means missing 90% of the game), or directly jump into pvp because there aren’t other options, and enter the “complicated - nowhere to learn - more complicated” cycle. The drama with mp every time there is a civ design rework is simply because there are no more sp contents to offer. Otherwise people would be busy trying them out in the new campaigns first.
It is the similar case with AOE4. Some people use the excuse “the majority of players are mp so no need to spend too much on making sp contents”——that’s because you never tried to make more and better campaigns in the first place. No wonder you don’t have sp players.
That’s for the well being of the game overall. From a more selfish perspective, there aren’t many high quality early modern RTS out there. Some people may just view this game as “yet another RTS” but it’s special for me. We have two medieval AOEs that largely overlap, and there are more smaller medieval RTS and even more medieval fantasy ones. I’m really getting tired of that. Early modernity is a rarely touched subject. I’m glad AOE3 made the effort back then. I know games like Cossacks and they are good. But they are published by smaller groups which do not have the resources to make modern high-quality campaigns with cutscenes and voice lines. AOE3 is the only one out there that has the potential.
Subjects like the hundred years war or the crusades have been portrayed over and over again by many medieval RTS. But can you imagine you can hardly find a good major RTS that covers the important early modern events like the Thirty Years War or the French Revolution? That is a huge missed opportunity.
EDIT: I actually think if there are still plans ahead, adding new civs does not have to be the top priority. We have 20+ very different civs now and old ones are made far more unique and diverse than before. People need some time to digest them. Adding sp contents (co-op also counts here) to catch up with the richness of civ designs would be a better move.