Hi guys, I created an account just to post on this thread. I can't say I've read EVERY post in this discussion, but I've read most of them. I don't think anyone has made my arguments yet. The general argument seems to be that there is less incentive than ever to build a "coastal" city (due to space requirements for districts and poor ocean tile yields), therefore making naval units almost irrelevant, which in turn makes building coastal cities even LESS valuable since you don't need a Navy?
While I'm on the fence about the value of building cities directly on the water, one thing I'm absolutely convinced about is that naval units will be MORE valuable than ever. The reason I think people aren't seeing the value of naval units is because we are still thinking like Civ V players, and not Civ VI players.
In Civ V you tried to build a coastal city on an inlet with as few ocean tiles as possible, or in a location with a multitude of ocean resources. Primarily you did this so you could concentrate the more valuable ocean trade routes in one city, have a city to build a navy from, and (to a lesser extent) build wonders that required you to be on an ocean tile. Perhaps you might have a couple of cities that meet these conditions, but otherwise you would try to build them so they were 3 tiles away from the ocean so you maximized your land tiles, and weren't stuck with useless ocean tiles. Maybe later on you would grab another coastal city in a relatively useless area (desert/ tundra/ mountainous area) to grab a strategic/ luxury resource, for strategic reasons, or because there was simply no where else to build. Since there were only a couple of "coastal" cities and some relatively worthless late game cities navies weren't that important. One thing you definitely didn't want to do was build a city 1, or even 2 tiles from the ocean, that had a lot of ocean tiles, but couldn't utilize them. How many times did you say to yourself "if only I could build that city 1 tile over so I could get that coal/iron and still get all of those ocean resource tiles, this would be the perfect city site", and you delayed settling there, and didn't settle there at all?
This led to the mentality that navies are only good for "coastal" cities, since in general inland cities would require a ranged attack of 4 and be out of range of most ships. Maybe you'd get lucky and have a tile in range or at least be able to attack land units. In general, there was a no mans land 1 to 2 tiles away from the coast were you just didn't build cities if you could avoid it.
As many of you have said, this is no longer the case. Your terrain is constrained by a number of factors, including rival civs, city states, mountains, dessert, tundra, swaths of forest/ plains. Like any good Civ player you will try to maximize the terrain given to you. This naturally includes ocean resources. So, you will now be placing MANY cities within 1 to 2 tiles of the ocean (maybe on a river to get the nice housing bonus), and MANY more cities will now be in range of your naval units. You want to build that harbor so you can trade from more ports and build ships in more cities. Those ocean resources right next to the shore are now much more accessible and you WILL build inland cities maximize their use. Maybe you build that city in that "ideal" spot 1 tile away from the ocean that you shied away from before because you can get the coal and still use all those ocean resources? Now Naval power is much more relevant. Frigates with a range of 2, battleships with a range of 3, a rocket cruiser (with say a range of 4), and aircraft carries now feel like they are able to project much more power.
But that isn't all. Another thing I haven't seen people talk much about is cliffs. Cliffs now create strategic bottlenecks on coasts, just like mountain ranges do. There are 3 ways to defend these. A navy, a unit on land (maybe in a fort), and a strategically placed COASTAL city. You will need an offensive navy to weaken all 3 and coasts are now more defensible than ever. Now since a navy is so important it DOES mater if your harbor can be pillaged while a city can't, and how many cities you can dedicate to building naval units from. The fact that it gets a healing bonus if it doesn't get completely surrounded is just icing on the cake.
As others have mentioned, with the housing bonus, the fact that coastal trade routes are likely more valuable (and far reaching), the ability others have mentioned to postpone building harbor districts till later, the eureka bonuses for research, and the fact that there is no penalty for the number of cities all make coastal cities just a bit more palatable.
Another factor that hasn't been mentioned is the city state dynamics. Naval trade routes can reach city states that are otherwise cut off by land and might have influence/ religion/ quest perks like they do in Civ V. Having that coastal city at the edge of your empire that can
just reach distant city states is valuable.
Also there are new coastal natural wonders like the Cliffs of Dover.
I do agree that some additional perks like faster ship building if your city center is on the coast, or maybe some select tiles (like reefs, kelp, coral or more abundant traditional ocean resources) would be nice.
On a side note, how awesome is the cliff scaling promotion?!? I want more scout upgrades. Like Berserkers (special unit for the Vikings), Conquistadors (Special unit for the Spanish), guerillas, Partisans (special unit for the French to replace the guerillas),marine, Gurkhas (Indian special unit to replace marine), special forces (maybe who also serve as your paratroopers), and Navy Seals (American special unit to replace special forces).
TLDR: There might be less incentive than ever to build coastal cities, but navies are almost certainly more important.