There are several impressions threads but they tend to talk about early game and not late game. So I thought I would help the devs fill the information void. I have played several games on hard that have gone on to like 200+ turns, even won a few. First of all the game is much improved over previous versions. Basically to sum it all up early game is fun and challenging but late game is boring now.
AI: AI is pretty good now. Some end up buggy and sucky, others are just slightly behind me in faction power. The big thing is that they aren't aggressive at all. In all my game no AI has ever gone to war with me! Probably because they are behind in faction power but still. Makes the game very boring if no one ever attacks you... If they are behind they should try and team up with allies againist you or use magic or other means to strike back if they can't beat you with military. If you declare war on someone they don't take advantage either, and they should. If you are allowed to just pick out enemies and kill them one at a time it gets very boring. You can also just diplo win with ease, even if you only have 1 more faction power then the next toughest team.
Monsters: Very nice! I love the new early game monsters, they keep you on your toes. There seems to be a bug in mid game however that stops monsters from spawning. This is also very annoying. Combined with unaggressive AI's this bug kills late game play. Game devolves into sim city, but even sim city had aliens and fires... Pls fix this! Also monsters need a way to spawn late game when there aren't many free forests left. I suggest randomely spawning monster lairs that push back faction influence and need to be attacked if you want to remove it.
Cities: I also like the new city building system, the only thing is some buildings are kinda in weird places on tech tree. Guilds are the main offender, they are a mid game tech that gives you super late game buildings that require level 4 or 5 cities. They are also a requirement for a lot of early game buildings. Which brings me to how ridiculous level 5 cities are. You need advanced housing and incredible amounts of food to get one of these(17 villas). I have won games way before getting them. I like that they are hard to get but you basically have to already have researched the entire civilization tree in order to get them, some victory conditions are easier.... By the time you get them you probably don't really need much in the way of resource bonuses. Also like it or hate it they hit the max city size and you need to demolish buildings to make space.
Resources: You should probably start with five more materials, because if you get unlucky at the start and don't find any you are at a serious disadvantage. Mid game however the great mill in itself gives you basically unlimited materials and it's easy to get. It needs a major nerf, right now it gives 12 materials and a 100% bonus. That means in itself it gives 24 per turn. How about 4-6 and 50%? While early game you can run out of gold easily, once you get a gold mine and some high level cities you start getting way more then you need. When they fix the gold tax bug this will be even worse. Other resources seem fine, except maybe the adventure techs that spawn mines or orchards now don't always seem to give you anything. Which sucks if the reason you researched it in the first place was you really needed some.
Armies: I like the new building requirements, but between the build time and research times they seem to really slow down army production. Meh. Also armor and weapons seem to jump up to much with tech. Early game units can't even dmg mid game ones etc.
Magic: I love the changes. So many more strategic options. Right now they aren't many late game spells, but I imagine they will fix this though.
Tech: Some tech trees are better then others. Diplo and Adventure need work. Diplo could use more treaties. For instance one that lets you share shards, in order to go for a magic win. You could also move the gold giving techs over from civ to diplo, like marketplaces. It would make sense and help even out the disparity between the number of techs in each. Trade is the way to make gold anyway. Adventure actually got worse because now it's resource techs sometimes don't give anything. Maybe move mounts and ships to adventure. Quests need work period, maybe in next big patch.
Stability: Early game is much better, but late game still suffers from bugs and crashes . My save file where I had a level 5 city even got corrupted ):
Dynasty: Kinda pointless as is. You don't really need to marry off kids to get alliances, and kids no longer start as channelers. Really need to add a system where kids inherit ,treaties break, heavily influenced cities rebel, and kingdoms split when the old dad dies.(maybe even from old age).