I played a fair amount of GalCiv2, and some pre-release GalCiv3, but then I completely dropped it until Crusade came out and there were all these reviews saying that it was a brand new game. And it is! I'm enjoying it more than Stellaris at the moment, and I really have to applaud how this franchise turned around. Haven't seen an improvement like it since... War of Magic to Fallen Enchantress 
It took me a bit, but I'm now holding my own on Normal. And frankly I'm not much of a power gamer and I doubt I'll ever be one of these people who play solo vs. 6 godlike. But I think that I'm part of a silent-ish (or at least relatively quiet) (or just not super loud) majority.
My gripes with the AI are not that it fails to overwhelm me, but that it makes obvious unforced errors
A short list :
- After culture flips, the AI's ships stay on the planet tile. They don't move away from it or try to invade it. I can move much weaker fleets nearby without them moving to attack it.
- The AI doesn't really build farms or cities. This has been elaborated in numerous "why doesn't the AI crush me?" threads.
- Ship role assignment / fleet composition. Because ships start in different positions, it's easy to defeat an AI fleet in detail without actually doing so.
- Aimless freighters and colony ships. Invading an AI empire or getting an exploration treaty shows you dozens of freighters not trading and colony ships not colonizing. At a minimum they should just be scrapped to save on maintenance.
- Overuse of defending legions. I'll admit I'm a little on the fence about this one. If the AI decides that it can avoid losing a war by dragging it out and not playing to win, I guess this is a smart play. But I've seen AI do this who definitely should have been fighting to win.
I hope this helps!
