Here's what I like:
-Huge fleets smashing into one another
-Asymmetrical warfare, needing to fight against a stronger opponent by taking advantage of terrain, positioning, using force multipliers to overcome the strength difference
-Generally speaking, streamlined macro gameplay, being able to churn out ships en masse and having reserves
Issues in AI War:
-The importance of micro - certain kinds of micro are way too good in some cases and pretty much necessary in others, the ship AIs are pretty dumb in general. Critical targets like hunter/killers and EMP guardians need to specifically be focused down in every single engagement if you want to keep your fleet alive. Plus there's no real way to know if your ships are doing things efficiently, if they're getting their bonus damage in, etc. It's practically impossible to play the game in real time.
-The blobbiness and mish-mashiness of fleets - your fleet always composes of every single ship type you can make - there's no way to specialize. Your fleet will always be stronger if you add more things to it - there's no way to make your fleet stronger against golems or whatever in a reasonable time scale. The best way to do things is either go on a thirty minute quest to find additional ship types to use or to just smash your entire fleet into it
-Lack of actual strategic or tactical options. Blobbing is way too effective, there's no collision, there's no real way to actually implement strategy. Flanking is pointless, surrounding is impossible, etc. There's no actual way to 'take advantage' of the AI. You just see if the AI has lots of ships in an area, and if you're stronger, smash them, and if you're weaker, send things elsewhere. It throws a wave at you and you stack turrets there. Oh? An exogalatic strike force is coming? Better reinforce that chokepoint with more stuff. There's just not really much that actually encourages real tactics.
-On a similar note, the AI hardly ever does anything or any action that is actually exploitable. I never really feel smart and think 'Aha! I got them there!'. The AI is way too predictable but also way too cautious. There's no way to actually goad the AI into attacking you, they just mass up in overwhelming force and take you out. There's no way to intelligently assault a fortified planet, etc. I think the game would stand much to gain from a more predictable AI that can be exploited.
-Turrets and mines. It's extremely tedious to plop down an your entire planetary quota of turrets and mines. There really should be an easier way to do this.
-Turrets and mines. They're stationary, but do they really need to be? It just makes things more of a hassle than they need to be. Just make them mobile defense bots that don't have warp drives or something so they can't cross wormholes. They'd be more effective obviously but I think they'll feel better if they were weaker but were actually more consistently useful. Often, enemy ships will just break through your line and run right past the turrets, making them pretty much pointless.
My (pretty radical) suggestions:
-Improve ship AI (this will probably happen anyway, obviously), make sure important things actually get attacked first. I don't want to have to target fire snipers with my own every single time I encounter them.
-Maybe remove the ship cap and put in some other system? The ship cap system is pretty emblematic of AI War, but I really don't think it does anything better than just having a supply system. It just means that your fleet will always be diverse and never specialized. Perhaps there could be a compromise, maybe you get a smaller cap for each ship, then some extra supply that you can then spend on any type of ship. So if I unlock mark II fighters, instead of being allowed to build 96 markII fighters, I can build 48 mark II fighter and 48 of any other mark II ship. This still keeps the whole 'ship cap' idea while allowing us to tailor armies to different circumstances. Maybe I want to go knock down a fortress - I'll just use my excess ship cap to mass bombers.
-Add some sort of collision? Currently, your ships can overlap with eachother infinitely, having a large fleet is pretty much the exact same to having a small fleet except you have more firepower and durability. Then, things like flanking and encircling might actually mean something tactically. There should be a meaningful way to make your weaker fleet be capable of defeating a stronger fleet due to certain circumstances. Things like an encircling or flanking bonus would be great. Maybe even a sneak attack bonus or something for ambushes! I think it'd be pretty cool to just power down your fleet and hide them, wait for an enemy fleet to fly by, then wake up in the middle of them and catching them with a surprise opening volley. I want to feel like I'm playing as an insurgency, fighting against a superior force with an inferior army and still coming out on top.
-Maybe change turrets into something like a defense fleet - they're local to a planet because they can't cross wormholes, they're stronger, slower, and have a per planet cap, and are less energy intensive compared to your mobile fleet. Defending should be easier than attacking, and having a large empire should be meaningful to stopping an AI advance. Currently, once the AI defeats your main fleet, you're completely defenseless while you're refleeting because turrets are completely incapable of dealing with anything in decent number alone due to their immobility - they just get killed from outside their range or ignored entirely. They're also entirely too weak to actually deal with anything other than small raids.
-Make mines a lower cap and just make it an attachment to a wormhole - when units pass through, they get damaged. Line placing mines on a world is a huge pain in the ass, and the worst part about it is that it's difficult to quantify its effectiveness. I have no idea how much the mines are doing. They could be doing a lot of work but I have no idea that they are.
-On that note, it would be pretty cool to have a 'kill counter' that tells you how many ships that your different kinds of forces have destroyed - such as your mobile fleet, your defense fleet (or turrets), your mines, your superweapons, etc.
Anyway, these are just some of my thoughts on some of AI War's core mechanics.