Well, that's ironic. I just got my fastest cultural victory (Emperor, t174) on the map most suited to the coast, ever.

Opposition was weak though. And yes, we're using the meme Ancestral Hall to overcome housing issues and I had by and large settled quickly enough so AHall was not important. think this is as favorable as it gets as it contains lots of space to take behind you, Nan Madol, and some hills. All land routes to attack me were through narrow mountain passes. Very little rivers for hubs, favoring harbors. So basically this is as good as it gets. Most of the inland spots suck though thanks to chopping still grew faster than the coastal cities, but hey who cares about those details. But.... it had the help of Goddess of the Harvest thanks to a lucky early relic which will be RIP soon.
Seed:
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I also uploaded saves, but the problem is the new CQUI apparently attaches itself to the save which means it won't work when the new patch comes out. Yeesh. I also think it won't work with CQUI either. So we need to deal with that ugly city display (good for functionality, terrible for screenshots)
Capital
So does that mean settling on the coast was good here? Why yes. I could boost shipbuilding and swim over to attack Dido, and used the infamous ship garrison trick. So the nature of naval domination did help, especially since Dido had attacked with Biremes. So being coastal here had its benefits as well as shifting my strategy. My city placement is awesome mind you.
Does that mean all those awesome fisheries and harbors helped? Well, no. I didn't even get Liang until later on, and certainly would not bother with wasting yet another governor promotion to get the other things. The harbor was the 5th district I built (I built an IZ over it.... though that is its own can of worms), because as we discussed before good coastal cities don't have that many water tiles.... so harbors don't make sense. Should I build harbors to miss out on these? Surely you jest:
Of course, most of the places didn't have good commercial hubs either. But even in these cases, can you really say I needed to build these harbors? I mean, it's a nice harbor, but maybe I should have chopped out another district?
Even a city like this which begs for a harbor, I still didn't do it, in favor of more practical districts And yea the campus is badly placed; sue me.
And this city has a harbor and is one of my biggest cities; but why the growth? Work grassland tiles?
A lot of this-- don't get me wrong-- does have to do heavily with chop = everything so that individual tile yields don't matter as much. This is what I mean by clear cutting your victory districts and whatever other stuff is really in the city's initial, short term development. This is why what most of the coast offers just falls behind in priority with everything else.
That being said, harbors aren't bad, of course and this happens to a degree with hubs too; gold is just not a victory condition so it's not needed to spam them everyone. Great Admirals can help but you do need at least quadriemes for those.
And of course look at these inland cities. They're not as populous, but the district yields (especially campus are higher thanks to the terrain features-- which kind of give you what you need to actually win and are far easy to manage (ie, I didn't manage them at all)
So yes, there are situations where coastal cities can be better; but it's far more situational that it appears and it is definitely not many of the reasons that are commonly stated. Don't think you're actually doing anything by rushing a harbor.
Also, the hall of fame says I won on t173; I dunno what's with that.