The biggest issue is not being able to identify buildings at a glance. The graphics are beautiful but don't serve the purpose of standing out on the map as well as districts did in Civ6. Even just putting accent colours themed on what type of building (economic, science etc...) would be a huge help!
This. The map succeeds as a beautiful graphic, but fails as part of the GUI in that it does not, at a glance, show you exactly what is in the tile.
I think the biggest part of this is not the individual buildings and structures (which are always going to be a problem given the variety of regional and Civ specific building types unless you simply color-code them) but the difficulty of telling apart Urban and Rural tiles. Maybe it's my tired old eyes, but they simply do not look distinct enough to me: clay pits, mines, etc look as built up and busy as any urban tile, and so the settlement/city seems to spread over the entire map.
I've struggled to get on board with unpacked cities and I think it's one of the main things that put me off Civ VI. The UI and design of that game at least made the larger cities interpretable in that game, but I feel like expanding your cities out with districts diminished the impact of geography.
I would argue just the opposite: the sprawling cities make geography even more important as you attempt to mine the 'adjacencies' that will best buff up your districts. This is the primary reason I argued back in Civ VI times against the adjacencies, which result in both sprawling cities and utterly unrealistic constructs (for starters, can anybody explain why a Mountain gives a bonus to a University, which would come as a great surprise to most of the early universities like Oxford, Cambridge, the Sorbonne, et al, none of which were built anywhere near a mountain).
I am not against multi-tiled cities as such - they potentially allow much more of the city effects to be shown on the map instead of buried in some secondary display - but neither Civ VI nor Civ VII does them very well.
But to make them work well will, IMHO, take more than just making the building graphics more clear and rectifying the adjacencies. For a start, Resources have to become moveable as much as possible. You cannot realistically move minerals, but a Rutabaga or any other animal or plant-based resource should not stop you from building over it, and either moving it or removing it as desired. No domesticated animal I know of is so particular that it demands a pasture on Tile A rather than the tile next to it, and if we want to make resources terrain specific those tiles are generally repeated in the basic biome your Civ starts in.
Having made Resources no longer an obstacle, we can then mandate that Antiquity Age cities can only put Urban tiles adjacent to the Center: everything beyond that will be Rural. In Exploration Age that can become adjacent to the Center or adjacent to a tile adjacent to the center. Only in Modern Age can you sprawl a city across the map, potentially building connected urban megalopolises of 10s of millions of inhabitants.
Keeping urban tiles 'tighter' both makes them more distinct from rural tiles and also brings in-game 'urban planning' more in line with Reality: the limitations of transportation technology that applied from 4000 BCE until the late 18th century CE (by happy coincidence, the beginning of the game's Modern Age) put a major brake on how big a city could be on the landscape and still function as a city.
Note that it also allows some very neat Civ Uniques like a city using water-based transportation to spread beyond the normal limits, such as Tenochtlan of the Aztecs in (late) Exploration Age, or
pozzolana-based Roman concrete which allowed Romans to build their commercial and residential structures up over 2 - 3 stories to pack greater density into their cities.
Properly designed, a game mechanic that allows multiple-tiled cities should enhance the gaming experience, not make it harder to accurately read the map and plan viable cities/settlements.
