A lot of this is showing some selective memory, or at least not presenting the FULL facts of the situation.
The Colossus was designed to be a Lucifer/Great War Shivan fleet killer. It also engaged a Sathanas on favorable terms and won. It's ludicrous to say the ship didn't perform, it was simply overwhelmed by a class of Shivan warship no one could have anticipated.
This. There's a trope from Tvtropes that also sums up the Colossus in FS2: Awesome but Impractical. I'll provide the full quote:
Awesome, but Impractical: The GTVA Colossus ends up being this despite the best of intentions. It follows a standard Terran design despite being co-developed by Vasudans; it can't project very much of its firepower in one direction but can engage multiple smaller ships in all directions at the same time, and is durable enough to win even if heavily outnumbered. This is exactly what the GTVA needs against the NTF, and is exactly what they could've used during the Great War. Unfortunately, the designers never imagined it would ever have to fight something of comparable size and durability, where its inability to deliver most of its firepower into a single target turns into a massive handicap.
This is exactly right. Remember, the GTVA had been fighting the NTF for 18 months with no end in sight until the Colossus was finally completed and deployed. As evidence that there was no end in sight at this time is this: just before the Colossus was deployed, the GTVA launched a two-pronged assault on Sirius that failed. Just after that, the NTF counterattacked in Epsilon Pegasi, causing more than 75% casualties to GTVA forces.
75%. As I understand it, anything over just 30% casualties to a military force is
devastating. (I don't remember the exact circumstances or when it happened, but I do remember a retired general being interviewed on the news saying this.) This proof positive that the NTF was more than holding its own during the NTF Rebellion so the stalemate showed no signs of abating.
But once it was finally deployed, the Colossus made short work of the NTF's fleet in Epsilon Pegasi, finally driving the NTF from that system. Shortly afterwards, Alpha Centauri, Deneb and Sirius finally fell to the GTVA. It's unknown whether the Colossus was redeployed to those systems and had a hand in those victories, but it's probably more than likely. So an 18-month statlemate was broken in a few weeks, if not mere days, by the Colossus. As noted above, this is its
intended design function: to take on multiple smaller ships at the same time and prevail even when outnumbered. Manwithamachinegun is exactly right: Up until the Sathanas showed up, the Colossus was functioning exactly as it was designed to do.
Command did have a plan to kill the Sathanas in the nebula using positing and tactics, it didn't work. The Sathanas evaded the trap and lure operation Speaking in Tongues. At that point, with the Sathanas barreling down on Capella, yes, it probably was worth throwing a destroyer in front of it to buy time. Everyone has a plan until they get hit.
Command didn't "let" Bosch open the portal. They had no idea it even existed. He was let go to allow SOC to continue their investigations and possibly recover ETAK. Which was stolen technology.
Basically there's a lot of basis of judgement on things we, the player, know, but Command could have had no reasonable chance of knowing. Other than vastly underestimating the scope of the Shivan threat.
Even allowing the portal to stay open was deemed and acceptable risk *because* of the chance of replicating the Knossos, to allow a return to Earth which would help heal all of human civilization.
+1 to all this as well.
No one knew the Knossos device was in Gamma Draconis until Bosch first discovered its existence at Deneb after he had partially conquered the system and plundered its archaeological sites during the NTF Rebellion. As for ETAK, Bosch had been gathering data on Shivan communication for years, if not decades, starting with him being involved in the fight against the GTI rebellion and him rising in the ranks to admiral just so he could get the GTI's research and build ETAK. Even during the start of the NTF rebellion, the GTVA had no (or perhaps a slim) idea of what the hell ETAK actually was. Some in the GTVA speculated that ETAK was a weapon of mass destruction long before it was discovered that ETAK was a Shivan communication device. All the GTVA Command knew was that ETAK was a project that Bosch was devoting all of his resources to. Thus if Bosch wanted ETAK that badly, then it was something that the GTVA needed to find (and acquire intact) pronto. That's why Command let Bosch go and lifted the blockade at the Deneb-Sirius jump node: because if the Iceni was destroyed then, so was any hope of discovering or acquiring ETAK.
Even at Gamma Draconis, the GTVA made the correct decisions according to the knowledge they had: They kept the Knossos device intact long enough to be sure they could construct another and destroyed it before the Sathanas could use it. No one (except genre-savvy out-of-universe players like us) could have predicted that the device would stabilize the Gamma Draconis-Shivan Nebula jump node even after being destroyed.