I've only ever played five and six so my perspective here is limited and I don't know if it was any different in previous games. But while I enjoy the games I've played, I've started wishing for some things:
- causa belli for a simple frontier war. Or trading boundary tiles in general. Sometimes my opponents beat me at getting a resource and I want a way to get it without having to take over their city and raze it to the ground (although that's always fun). Peace agreements should let you nudge the line, or even force your opponent to make huge territorial concessions without necessarily ceding whole cities. I know this is supposed to be done with cities but taking on the tile granularity might be met with less warmonger penalty etc.
- Allow wars for influence on a city state. Sometimes I go to war with a civ and don't want to take them off the map but just get their capital, peel off their encroaching cities, etc. That ends up fine but at the end, they still have all their envoys to city states that I've been wasting all my envoys on! And that gets extremely annoying. So this is a two parter. The first is that you should be able to trade influence on the deal screen. This actually incentivizes you to gain influence in city states whose focus you're not interested (faith, culture?) because that becomes a commodity you can trade to people who might actually want that influence. the second is straight up that I want to go to war with city states and upon defeat, remove all other foreign envoys. That kind of sphere of influence stuff is definitely the predominant kind of military action anyway once you get past the Renaissance era in history.
- speaking of influence, rethink economics in general. food, productivity, and currency aren't totally independent things. Food is exportable! Trade routes to other civilizations should also bring with them food surpluses. Trade routes within a civilization should produce just as much wealth as trade routes outside of them. The principle benefit of trading between civs should be in increasing friendliness, religious pressure, and mutual science and culture boosts, but the material advantages should be the same. As it stands, while I *can* make cities in, say, agriculturally desolated but minerally rich areas (Arctic continents and islands come to mind specially), and just send trade routes with food, in practice I always use my trade route capacity for coinage. If this trade-off was intentional it wasn't thought out. Making food exportable would also create really interesting situations like on civ being dependent on another breadbasket civ, being able to starve civs as a war strategy (blockades, so on... although I remember that civ 5 had blockades as a ramification of its capital city connection mechanic...
- pls bring back Venice
still love the game though