I wrote a handful of notes when Lucy OpenDev was live but never actually had time to type them out for devs to read. Some of my thoughts may no longer be relevant but I hope they can still be useful.

Culture specifics:

1. Harappan - Canal Network. The UI shows unusual levels of exploitation changes when placing new districts adjacent to the Canal. This might actually be from any 'free placement' district such as City Centre, Administrative Centre, Hamlet, etc. but I noticed it the most on Canals.
2. Carthage - Legacy Trait. -50% feels excessive and very strong to last the rest of the game. Especially compared to (or combined with) Phonecians -20% in the previous era.
3. Franks - Scriptorium. Less powerful than standard Research Quarter due to less inherent Science and hard to obtain adjacency bonuses.
4. Huns/Mongols - Embarked units with "Free Rider" trait get the double attack as embarked ships. Unsure if intended but felt quite strange to play with.

Culture Traits:

1. Playing with Expansionist Trait. Enemy AI cares too little about having territory stolen. I claimed all possible territory (all attached territory - none of the cities) on home continent and my two allies forgave every instance (leaving them with 3 and 5 territories each). Non-allied AI generated grievances but none of them declared war or tried to stop me stealing.
2. Playing with Militarist trait. For a Trait that's meant to encourage good warfare the ability to instantly produce 4 weak units does not feel great - especially when Population is the largest limiting factor of armies (more on that later). If they had a combat strength bonus it might be enough to feel worthwhile but I can't see when the addition of 4 'defender' units could swing a non-defensive fight.

1. World Wonders - Hard to find the list of where to pick a new one after the initial 'tutorial' pop-up. Also I think they have too many effects that do lots of things rather than 1 solid benefit. Equally unclear how Wonder Explotation works.
2. Machu Pichu is an exception to the above - It is incredibly strong at one thing. I built it in a high food city and now every city in my empire has a bonus +122 food. 

1. Population growth. Population is king as it impacts all city yields AND military. Enemy AI often has very very low pop cities due to creating numerous armies, which hampering their output and resulting in an AI with a greatly reduced capability to impact the game.

   Also, pop growth gets out of hand after a certain point and cities never slow down growing, even after the pop limit is reached. My capital was at 41/31 and still gained 1 pop every turn (with Frankish Legacy Trait and Abundant food). Some form of diminishing returns on growth may be needed.

2. Retreating army - It is hard to pin down enemy forces as all your units in a large radius have their movement set to 0. It might feel better if you could control which units were considered part of the attach before the enemy can retreat.
3. Immediately after capturing enemy territory you are able to spend gold to heal - it makes defending after an invasion very easy. Also, cost of healing units is either too low or needs to take additional turns to apply the healing.

4. Embarked Movement is also very slow - cross ocean invasions/exploration feels tedious. Possibly matches reality but made for a very sluggish midgame invasion.

5. Illogical progression of Civics. I unlocked Scientific Facts and Irreligion during Classical era yet Knowledge Authorities didn't trigger until Early Modern. Should possibly be an Era Requirement/Limitation on some Civics?
   

6. Trader Fair (Mercantilism Tech). 4 Money is absurdly low for a late game tech compared to other money gains - especially as it is a constructible with multiple other requirements.
   

7. 'Occupation' Status on cities is not explained in the UI anywhere.
   

8. Stability remains an unnecessary consideration around midgame from all the Luxury resources and wonders. A possible fix would be not allowing all copies of a luxury to affect all cities in your empire - maybe only a certain radius that increases with techs?
   

9. Trade Routes - Need to be able to see them for Dutch VOC Warehouse. It gets bonus Money if placed along a trade route yet you have no way of seeing where that route might be.
   

10. Pillaging - I had a boat going back and forth between two Pearl improvements constantly Ransacking them after the AI would continually rebuild. AI issue with 'safe' building logic and no attempt at sending units to prevent it.
    

11. Enemy AI does not understand being sieged. Feels like they should be willing to remain in defensible cities where they can't be damaged rather than attacking the surrounding units and lots of damage. I took a few cities that would have been otherwise impossible to capture because the AI used their defending units to attack.
    

1. Embarked Unit movement count is off. Consistently said move limit was 3 after (unknown Medieval tech) yet I was able to move 4 hexes.

2. UI behaves strangely on relocating outpost. Always claims a gain of 2 food, 2 industry regardless of the yields of tiles involved.

3. I defeated an enemy AI to remove it from the game. This generated a grievance against one of my allies because "I surrendered to <defeated AI>".

4. Horrendous Sound issues starting around turn 100. Likely caused by too many sounds trying to play at once and they all become broken and tinny at start of turn. Possibly personal graphics settings at fault but no way of verifying.

5. Pillaging - I had a boat going back and forth between two Pearl improvements constantly Ransacking them after the AI would continually rebuild. Issue with 'safe' building logic and no attempt at sending units to prevent it.

Tenacal wrote:

• Illogical progression of Civics. I unlocked Scientific Facts and Irreligion during Classical era yet Knowledge Authorities didn't trigger until Early Modern. Should possibly be an Era Requirement/Limitation on some Civics?

I don't need some well-known professor to tell me God doesn't exist to be irreligious, nor do I need them to tell me that all things fall at the same rate, before air resistance is applied.