The game mechanic that invokes that is some sort of "see how long you can survive/defend the objective" last stand horde mode, but that doesn't work well in Elite (installation scenarios) and with the specific kind of fighting interceptors take to bring down. It also wouldn't lend itself to making the thargoid combat more accessible so it's understandable why they couldn't do that.So how do you get to a point where that might be a reasonable possibility when at no point do the players visibly lose. Just translating the tactical results faithfully to the strategic layer always ends up in a week 1 total defeat for the Thargoids (or month 1, anyway)
There are also threat mechanics in strategy games where you need to fight back in moderation without ing off the Omnipotent Enemy too much or they'll crush you (AI War, Terra Invicta), but those also don't work in a MMO environment where letting the players do "the wrong thing" could result in incredible toxicity.
The balance needs to be incredibly precise if the only lever they can tweak is how much player contributions push the bar across the board.
If the simulation was/is more complex behind the scenes then it should let imbalances develop along some sort of front line and open up the possiblity of strategies emerging.