AI, both majors and pirates, make decisions, act and react both DURING my turn and AFTER my turn, but my fleets cannot even instantly attack enemy fleets they intercept during 'end of turn' sequence. 

How is this supposed to work? Is 'execute orders' button bugged as it makes all ships act instead of only your own? Is this RTS with pause or TBS or what? How do you play this? AI responds to my actions basically in realtime, but I can't do the same. I cannot unfold any strategy, disband damaged fleets to repair them or invade effectively on even grounds. I can, of course, build a stack of doom or rush maxed tanks and faceroll the AI but it got stale pretty fast. It's basically playing chess where your opponent gets to move two pieces per your single turn. You can't effectively 'outplay' that. It's not that I can't beat it, I did win 1 vs 12 Craver derby on Endless but that was a chore, not a challenge. Achieving that victory was not a satisfying 'game' experience.

This can indeed be annoying at times. Esp. when it comes to fleet actions where timing really matters. 

One thing that helps a bit is to disable some of the popups. So, when a new turn starts and ships need to be sent away as fast as possible, you don't have to right-click yourself through a dozen of these. 

I think it's probably better to take your turn 'after' the AI has finished. It's more frustrating in multiplayer, where the race to click could still happen and grant a decisive advantage. (Players are unlike the AI, who will graciously always take their turn first if I wait, and doesn't seem to run a fleet away as one of mine arrives.)

Some way to mitigating this would be to lock fleets in combat until retreat, like ground battles. There is no idea for this I can find, but someone may like to create one.