Sostratus
Deity
I think the research resources of a civ type game, whatever they are, should be designed in such a way that you don't inherently limit empire types over the primary phases of the game. (Ultra late game where a player can "max out" everything is a different beast entirely and that's like saying coastal cities are strong because you can get seasteads+offshore wind on every sea tile...) This can be through the resource itself being limited in some way or through the modification of the research rate by playing with costs too.Campuses spam is not good for the game generally, and is the main thing that pushes the game to be a bit more “wide” than it should be.
To me, Culture (and Gold) should be the yields maximised by wide; and Science (and Hammers) should be the yields maximised by tall (with maybe some Science from Trade). But Campus Spam (and how it interacts with City States) makes both Culture and Science about wide.
There should be a break or limit on Campuses. I’d like to see empires only able to support so many globally, rather than automatically one per City, and each Campus and it’s buildings then also being very costly to maintain. I’m not sure what that “global campus capacity” should be based on though. Perhaps your overall empire wide Population, and then adjusted by other things like Government Tier, Wonders or Great People.
I think the +50% for 10 Pop type cards, particularly Rationalism, need a rethink. It really does just push you to have Campuses everywhere and every City at 10 Pop and no more. Although, if you couldn’t spam Campuses in every City, then Rationalism specifically might not be such a problem anymore.
ANYWAYS
As for resource advantages of tall v wide, the biggest issue in civ6 is cities essentially "cap out" in an area once the district is built. There's no opportunity to invest further. Without getting too ridiculous, if the "building tree" for cities was deepened at all stages of the game, then you'd have much more emergent diversity in games. You can't really build up Rome to a peerless imperial capital, and you can't intentionally create a true megacity like NYC aka "Meierhattan" because the next town over can also just have a bank and a shipyard. So once I get my win districts down its time to prepare more settlers.
I do think that we need to recognize that a tall empire should always lose to the same tall empire + a chunk of moderately developed cities for that era. Because the latter is literally "better." Doesn't have to be linearly superior but it shouldn't be worse. When you start making it so people leave the map empty, that's when players get roiled. Even in civ5, though, you could still leverage wide (though you needed religion.) It turns out a 4 city tall empire was critically weak to someone with competent ICS rolling in 20 tanks...
I think districts and district adjacency is one of the best things about civ6. And the district adjacency works very well to do what it's designed for: players placing districts in high adjacency tiles.Well, I'd say that it's more of a symptom of a disease. Districts with adjacency bonuses were a cute idea lifted from another game, a game where city spam is well-checked. If you have game that lacks regulatory mechanisms for expansion, and then you set up winning conditions that reward specialization, what do you expect the player experience to be like? if you can rack up an adjacency bonus that eclipses the value of a library, you're definitely front-loading a low-pop city. Forget the library, go find another mountain range
The true problem of district spam is that the buildings are just so much better than the adj for everything except the Harbor+IZ, and then the building cards compound the issue. There's no scenario where it's a bad idea to throw down a campus, even in the middle of the snow, because you can just dump out the buildings and rationalism will hand you the pop equivalent science of a size 20 city. (Campuses have too many good sources of adj right now, though, that I agree with) Even though the harbor district, as an example, has phenomenal adjacency benefits, it's uncommon to build a harbor in a one tile lake in an otherwise landlocked city. Likewise, unless you need the factory or power coverage, building an IZ at +0 doesn't really make sense right now. Ideally districts would only go where they have good adj unless you were focusing that area specifically.