Open wide

Ferris asked the other day if there is anything in Civ 6 that constrains an empire going really wide by building lots and lots of cities everywhere.  You can always build more settlers and conquer more territory, but the question of whether or not this is a good idea is another thing entirely.  In previous Civ games there were things that kept massive expansion in check, ranging from corruption making far flung cities unproductive to income penalties for each city to global happiness preventing growth.

Civ 6 has things that curtail growth and expansion, like all previous titles.  The difference is that those restrictions are trivial and growth is always correct, whether it be peaceful growth or conquest.  The thing that is obviously supposed to stop growth and snowballing is Amenities.  Unfortunately Amenities don't do the job at all.  Each city gets 1 for free, which encourages going wide.  High population cities don't actually deliver much more in the way of science or culture than low population cities but they do suck up huge amounts of resources in terms of housing, Amenities, and food for growth, so you shouldn't bother building up cities.  Just make new ones! 

Each new city gets that single free Amenity, plus it can build more copies of districts you want, plus it gets its own base tile for free, plus the free Housing from location.  You even get to grab new territory for extra resources of all types.  All of that means that a small city say up to size 4, requires basically no infrastructure, gets to build copies of superb buildings like Monument / Library / Market / University, and then can just start pumping out another Settler to make yet another tiny city doing the same thing.

Conquest is even better than settling though because not only do you get cities that already have stuff in them, you also take stuff away from other players.  The same sort of calculations apply, and although you do end up with cities that have suboptimal builds because the AI made them, you get to pillage the land before conquering it which gives you a huge boost.  In theory the grievances system stops endless conquest because people will hate you, but in practice it is not much of a problem.  You just keep on warring with one enemy at a time, leave them with a single garbage city at the end of the war, and watch that city flip to your control via the loyalty system.

Never stop pumping settlers, never stop warring with whichever neighbour seems most juicy.  Expand until the world is yours.  There is nothing in place to stop you.  Doing this will often lead to your cities running low on Amenities but that actually doesn't matter much because the penalties from not having enough Amenities aren't nearly as bad as the penalties from not having all those cities.

So the tall vs. wide debate is simple:  No matter what victory condition you want, you go as wide as your military can manage, and never stop. 

I don't think this is a good thing.  It encourages snowballing, and means that a good start, or a lucky victory, leads to a world spanning monster that can't be beaten.  It means peaceful games are just foolish games, in terms of winning.  It also means that you shouldn't worry that much about city placement, just jam them in there as much as possible.  I get how some people would like it, but it isn't to my taste.

So how do we fix it?  (Hint:  Not easily.)

You can reduce the benefit of spamming Settlers easily.  Ramping up Settler and Trader costs, reducing base Amenities to 0 instead of 1, and making Housing easier to get are good starts.  You can also make the high end buildings good instead of rubbish, which matters because only big cities can really scrape together the production to build them.  Right now those endgame buildings are garbage, which makes a big city not have much to do because you can only build 1 copy of the high quality early game buildings.  Making specialists good instead of worthless also helps because it means that huge cities can leverage their big population to do specific things - I have modded Specialists to make 5 of their thing (or 10 gold) and suddenly they are really worth using.  Changing all of that stuff makes growing big cities a lot more appealing and spamming crap cities much less so.

But that doesn't fix war.  If Settlers suck, then just build Swordsmen instead and take those cities from the AI!  This is a way more challenging thing to tackle, because the AI is just terrible at war.  I can't fix that, so I am limited to patching the most obvious holes.  Getting rid of Professional Army, which reduces upgrade costs by 50%, is a good start.  This prevents players from trivially rushing to a new unit, upgrading en masse, and crushing the AI.  However, players also use unit XP and healing so much better than the AI it is a serious concern.  Slowing the rate of unit XP gathering or reducing healing rates would dramatically benefit the AI and would make sure that player units die and must be replaced.  That is the core of the problem - player units never die because of superior play, careful healing, and levelling up.  They end up with a massively highly promoted army, while the AI continues to use green troops that they pay full price for.  Break that chain, and war becomes drastically more of a challenge.

Going wide being superior is so deeply entrenched in Civ 6s systems that it is a really hard nut to crack.  Moreover, if you punish going wide too much than AIs that conquer or settle too much territory could respond badly to it and completely fold.  However, it is a thing worth attacking, because right now high difficulty settings are all about the AI getting ridiculous early game bonuses, the player barely surviving, and then in the late game the AI just screws around being an idiot and the player cruises to victory assuming they lived through the early assault.  That isn't satisfying, and I am sure I can do better.