I am a very defensive player. (I've only played one game, and not even finished it at that, but 14 hours is plenty of time to recognize your play style.) This ends up leading my game taking way longer than it should, as I am constantly doing things like draining my economy trying to get a SuperFortress built on my homeplanet, and also pulling my fleet back to defend against waves. (Okay, I admit, the SuperFortress is just for the lulz.) I can't seem to defend adequately with just turrets. I know I should gate raid all but one warp gate, so I can concentrate turrets there, but there's a couple problems with that.
First, one of my AI's happens to be the type where it builds a black hole machine on every freaking planet. This is very annoying to deal with, as I can't just destroy them or it gives +10 AI progress. It means any warp gate raid is a one way trip for the ships that are raiding.
Secondly, ships keep streaming into my planets that I don't have warp gates near. I know in theory I can defend those with just a few turrets here and there, but the ships are often mark III and IV, and the few turrets I can spare is not enough to defend all my planets.
So, my fleet often is sticking around helping to defend instead of off attacking. It seems like I just send my fleet into a planet, ready to take it out, when a warp is called full of Zenith Bombards on an inadequately defended planet, and my fleet is stuck where it is because of a black hole machine.