It's on post launch when they are more focused on trying to earn back people that they already lost, like me, instead of trying to improve the game for the people that are still there.
I'll not purchase Civ7, and therefore I'll not purchase any Civ7 DLC. Any effort they put in trying to make the game more to my taste now is wasted effort, as the changes required would basically be re-making the game from scratch which is just absurd.
They should instead focus on making the game better for the people that are playing Civ7 - the players that actually enjoy civ switching, eras, etc. Polish those ideas, make them the best possible version of them. So that these players might have incentive to buy the DLCs and have a positive experience with the game.
I don't like the whole "games should follow what the majority want" idea that seems to be the popular one nowadays.
Most of my favorite games are niche games (heck, my favorite civ game is Civ4Col). Those games I like wouldn't exist if their developers kept trying to design for mass appeal.
Let the people that enjoy Civ7 have the best Civ7 they can have. We can always have other games.