I tried fighting the Shakturi for the second time and I just dropped it because of what a mess it was.
I literally could not counter attack and siege their world because they kept sending fleets and my fleets were busy fighting them. Then I ran out of fuel because they didn't have time to fuel because of the constant attacks.

Shakturi ships are so absurdly strong that you can't fight them one on one, but you can't outnumber them because they keep spamming ships. You can't tech up to meet their power level before they show up because the game's research system is silly and makes most of your labs useless at a certain point.

You can't use hit and run tactics because they'll just rebuild their mines and they have so many credits and resources stocked up. Their bases are pretty well fortified so a harassing squad of frigates, which usually does the trick, can't destroy them quick enough.

I honestly don't see how you can beat them without meta knowledge and just nuking them when they show up as refugees. It just doesn't seem well designed. The game is too easy without them but impossible with them, I have no idea what the devs were thinking when they designed them.