Civ4 was good at making goverments discrete systems to choose from which are simple yet have massive importance, defining the empire - but it was too simple
Civ5 was good at tracking player's empire changing across ages and accumulating cultural legacies, it was rewarding commitment and good choices - but it was too static, inflexible, blended gov system into one with culture and policies
Civ6 was good at being flexible, offering a lot of options and choices and separating gov from culture and policieis - but it was too fickle, there was too little commitment and too few difficult decisions
So I hope Civ7 achieves the synthesis of everything best of those three games, avoiding bad stuff