Playing for quite a few number of hours as Germany in the campaign here are my thoughts:
1. Aggressiveness - I know its been brought up but the AI aggressiveness is just absolutely terrible. There have been convoy defense missions, that is the AI attacking my convoy, where the enemy just runs away. Going further into this topic it doesn't seem or feel like winning the convoy missions, as the attacker, has any relevant impact. Does the number of transports destroyed lower the enemy transport by that much? I know that unless I destroy warships I get literally no victory points which also points to horrible design. Finally it seems my fights with the AI ALWAYS end up with the AI kiting away.
Fix: First make better decision making for the AI. Second make convoy missions have more impact. Third, and this is a bit more complex, I would use the weight system, so that if an attacking force is roughly equal or superior and they disengage it results in some loss of victory points. (Similar to losing morale at not being willing to fight.) I.E. 2 CAs 1 CL and 2 TB's attack 2 CA's 1 CL and 1TB and they disengage they have a negative impact. The flip side being if something like 3 TB's attack 1 BB, 1 CA, and 2 CL's a disengage has no negative impact.
2. Victory points - in my 1890 gameplay the British are just gaining VP's each turn. Why? even when no transports are sunk it seems to go up. We have roughly equal fleets and the only further problem is that over half the battles they simply run away.
3. AI - It seems that the AI cheats, that is that the AI knows where my ships are and if they choose to run away its directly away. I don't mean either that they know the general location but it always seems to be exact. Add in to this accuracy, I have noticed where I have shots with 40 - 60% accuracy and the AI has 10 - 20% with the same guns (say 7in). The AI will often end up getting 10 hits to my 2. I understand random chance but with the frequency it happens I have to question if the UI hit chance on the guns is wrong or if the AI has hidden bonus modifiers.
4. Player impact - Despite having most of my ships active the impact I, as a player, have on many of the facets in the game, like economy and often even losing transports, seems like its lower than it should be. Transport wise, as I have said, I have roughly an equally sized fleet but losing many with no convoy battles makes me feel like it often doesn't matter what I do. (tried having all ships on sea control, in being, and even splits just for testing.) I understand the realities of things but as its a game it would seem better to find a middle ground.
5. RESEARCH - The research system is trash. I am sorry because I love the game but what makes it trash, to me, is how poorly the priorities are handled. I know this has been said so I will leave it at that for complaining.
Suggested fix: I would either make it a 30 - 50% speed increase and a 2 - 5% speed decrease for everything else, that way it feels there is a positive gain to using priorities, or else just make it a lower 15% (ish) increase with no downsides.
6. Campaign start - When scrapping ships before campaign start it only gives a partial refund. It would be a nice QoL if it gave a full refund. Note: It goes without saying that this would only apply to before campaign start on custom fleet builds. It would just help if you misclick and build the wrong ship. I.E. You build BB's and then go to build CA's and accidently build more BB's or the wrong CA class if you have multiple classes.
7. Dockyard improvements - It doesn't seem like it makes sense for the current dockyard size increase. Its a linear growth in that 500 tons takes 6 months and 5m and 2000 tons takes 24 months and 20M. It becomes a clear benefit to go in 500 ton increments for immediate use, if needed. I think it would be better to give pro's and cons. I.E. do 4 projects of 500t increases at 6 months each, offering immediate benefits every 6 months, or a 2,000t increase but the benefit its say a 3 or 4M cost decrease and 2 - 4 month time decrease.
8. Enemy TB's - Almost forgot this one. This kind of ties in to if the AI has hidden bonuses, which they do they need to go, I don't understand how first off straight HE is overpenning from things like 4in guns. The enemy TB's take TONS of hits, almost flood then a few minutes later they are back to full float ability. Just to give an example of how ridiculous this is. I manage to get 2 flash fires back to back on the same TB.... it pulled off and didn't sink. Meanwhile my TB's, with an exact replica design, sinks 5 times more easily. So I am not sure which way the problem is but it has to be resolved. (Note: I have used CL's with 4in, 5in, and 6 in as well as CA's with 7 in and as many 4,3, and 2in as I can and no matter what the same issue occurs.)
I won't number this but I sometimes get weird issues where a ship will be maneuvering, sometimes only slight adjustments, and it will take a huge slowdown for no reason while other ships doing similar/same maneuvers don't.
Overall I appreciate your work and effort but wanted to give my feedback after many hours in the campaign.