Arpit I wasn't saying that the GTVA was capable of destroying 80 Saths. But 80 Saths CAN be destroyed, provided you have the ridiculous amount of firepower necessary. And that was made clear, by the very fact that you destroy a Sath fairly quickly (chronologically speaking) after encountering it in the campaign.
The thing that always made the Lucifer so menacing to me was the fact that it didn't matter how much force the GTVA brought to bear. It was just invincible. It made fighting the shivans different from fighting anything else. It was like fighting an elemental force, not a sentient enemy. the Lucifer was there for most of the game, reminding you that no matter what you accomplish, you still lose. We don't get our 80 sath deathblow till near the end of the FS2 story arc, which critically changes the atmosphere.
I would argue that the loss of Capella while scientifically more devastating (in terms of sheer destructive power), is no where near as bad as the loss of Vasuda Prime, or what the loss of Earth would have been. Densely populated or no... it's just a colony. Not the homeworld.
The systems you listed. All the NTF ones I don't really count. It was a rebellion. Civil war. Different feel. It was hard to get a back to the wall feeling when fighting the Shivans when only two of the systems we fought them in were in our space, and only one was even useful. That's nothing like hearing 'The Shivas wiped out our major base in Ribos', 'We've lost all contact with our forces in the Ross 128 system' or 'we've lost contact with every outer colony'. The Shivan advance waltzed into our core systems and blasted everything in its path all game long.
Furious war or no, when half the war takes place on enemy soil, the stakes aren't as high.
For most of FS2 the GTVA feels like they're winning - or at least giving as good as they get. Just cus they turned out to be wrong doesn't change the overall feel when they think they're winning. I'm not saying FS2 is bad, I'm saying the atmosphere is fundamentally different, and that it doesn't hold a candle to the atmosphere of FS1