That our military and weapons technology is largely superior to theirs might make sense in that context
Military side/strategies maybe, but technology?
The only reason we’ve been able to hold much of a candle to it is because of the magical Guardian reverse-engineering that occasionally pops up every once in a while.
Actual self-developed human weaponry has barely seen any development, and it would’ve been quite a while until anything better than our current peashooters came out of that. Try those against a Hydra or Medusa and you’ll know how inadequate they are.
Titans were also completely impervious to assault until the nanite magic that somehow isn’t affected by the AGF(no reason given) appeared.
The existence of said technology in Guardian relics being an established factor prior, but everything else about it doesn’t seem particularly believable. Like that the Thargoids are somehow completely oblivious to it despite collecting unclassified relics when prompted (encouraged with the threat of destruction) to drop them by neutral Interceptors, which are made
in their own derelict structures. And those are not so derelict as to have lost their connection to the rest of the Thargoid “network”.
Plus the idea that they decided to fight a conflict on oddly human terms instead of with the capabilities they have available, and, mostly ineffectively, contest the same systems while leaving the orbital/surface infrastructure in a poor but still repairable state. Whatever stopped them from moving Titans a few light years inward every now and then, after thoroughly wrecking a region, when they trawled through empty space for months to reach human space… I doubt it’s capability and more to do with will*.
As for their inability to adapt to humans…
It's very likely that as far as the Thargoids are concerned they were still fighting Guardians in their thinking and never managed to adapt to human tactics and psychology,
… in conjunction with my response to this, the Scythes could be seen as one contrary example to that idea, because those of us who actually have functioning brains without sociopathic tendencies, unlike some of our leaders in the Bubble - right, Hudson? - probably don’t find the act of those abductions particularly enjoyable or approvable(?). A psychological effect more than one of showing brute military force.
Of course, then Aegis decided they’d done enough to rescue people and just sent the rest of them to the scrap heap with the Titans. So that’s not something I could use as an argument further.
*I could also just be giving the writers too much credit here by assuming they have the Thargoids deliberately holding back in what they
could be doing, and instead conforming to a “traditional” style of assault for no obvious reason(to our monke brains), as a test of sorts.
What for? Well, only the Queens know. And I don’t think they’re too inclined to tell, unless they come out and throw a sign at Seo saying “Good job blasting our Titans that we put out there as target practice for you, we needed a bit of war warmup”.
As it is, the story is on ice because of a - presumed - variety of reasons but because the sacred Powerplay rework clearly cannot be delayed, apparently, the Titans are just getting blown up unceremoniously, Aegis has stopped bothering with the research it said was core to its new iteration, humans still celebrate and think everything’s going to be fine with nobody looking at the past history.
If they wanted to mess with us for a bit because mecha-Salvation is bringing some Constructs for company, I feel like there’d have been better ways to achieve that instead of throwing eight Titans under the bus. Can’t really see what that is supposed to achieve.
