I've had many moment in the game when I felt like quitting. Whenever I wouldn't understand a game mechanic, or strategy, or progression system, design decision, etc, I would just feel like quitting the game, that it's not worth my time and it's just a bad game. But each time I took a step back and started investigating what exactly is bothering me, and if maybe I'm the one looking at it wrong. Sometimes reddit answers helped me, other times youtube videos, or discord, etc. Here are the things that kept me from abandoning the game:

-Geospace activities are fun. Exploring, trading, unlocking and building bases, defending against the Behemoth, finding Antedeluvian sites, etc

-I finally understood just the other day that the game's equipment progression is not like in Xcom. All you need for a long time is faction armor and weapons which is basically the Tier 2 equipment (Tier 1 being the starting Phoenix Point equipment). All 3 factions are more or less on the same Tier with the equipment, although each has it's strengths and weaknesses. And then there's Tier 3 which is the Antedeluvian equipment. Still haven't used it too much but that's what I found online, that it's basically Tier 3. What I don't know is where does Kaos equipment fit in. Might be a 2.5 Tier or maybe just as good as Tier 3 I don't know yet. Only you need to not rely on them too much. Have each soldier with a Kaos weapon AND a normal weapon.

-Understanding diplomacy is also a game changer. I finally understood that an effective way to go about diplomacy is to get a faction to Allied status while trying to keep at least one other faction friendly so you can trade. 1 faction is not enough for profitable trades, you need at least 2, and 3 is even better, but that's very hard as my strategy is to steal aircraft from one of the factions. Usually the one that is most hated by your allied faction. But I'm hoping I'll manage to get the 3rd faction's diplomacy back to trading status eventually.

-Understanding the game's goal. The goal of the game is not to save everyone. You don't need to save every haven. At first it's quite impossible to save all of them. You'll see as you explore the map that there will be sites of destroyed havens that you didn't even know about. The only reason you don't care about those too much is because you weren't alerted about them, as they were not discovered yet. You goal is to stop the "bleeding", eventually. You can get eventually to have multiple teams around the globe and be able to respond to all haven attacks, but until then you will have to accept some haven losses. You could also beeline to the end of the game I'm told but not sure about that. Could be risky as to advance in the story to a difficulty too high for your soldier's level and equipment. So for now I'm just continuing to develop my bases and especially antedeluvian sites, while defending whatever haven I can and completing other missions and exploration based on proximity. Finally when I will feel that I have topped my soldier's readyness and equipment I might start prioritizing for the story missions and complete the game. BTW don't avoid them if they're close, they give some rewards so are worth doing.

-And finally, understanding all of the nuances of the combat missions is also very important. I have yet to master it, but I think I've become somewhat decent at it, but I might still make some decisions that gets someone killed, and this leads me to my last point:

-Don't feel bad for save scumming now and then. Don't make it a habit as that devalues your decisions and immersiveness, but don't feel bad about pressing f5 before making a risky move, like not taking cover properly, or not taking account of the specific danger each enemy poses. I call those "learning moments" and don't feel bad about reloading. Once I lost a soldier because I didn't expect him to be able to be one-shot, so I let him a bit too open. I reoaded lerning my lesson to not underestimate my opponent. On my second playthrough I think I'll stop doing that but I think it's still good to do it if you spot a learning moment. If you ever wonder... "hey what happens if I do this?" just F5 and try it, you'll learn something.

Disclaimer, that I haven't yet finished the game so there might still be things down the line that I don't know about yet. Hope this info helps you to keep enjoying the game like it did for me. Also I'm playing on Hero difficulty.

Now if I could only figure out if haven military strength has an effect on Steal Aircraft missions, does anyone know that? I somehow feel like it is ignored as that could suggest some unhealthy gameplay (waiting around for ships to go to low power havens, which they might never do and you're just wasting your time and fill you with regret).

Sure Phoenix Point is still rough around the edges. I think they should have continued polishing it. From in-game tooltips and game mechanic entries (like for the military power), to combat mechanics like cover, stealth, aiming, overwatch, animations, etc. But it's still a good game worth playing one playthrough.