I've watched as many vids as I could find on YouTube re: Encounters with the Ships (Thargoids).
One thing I've noticed in all - not a single incident showed the ships (Thargoid) actually attacking anyone - even if the encounter was up close and personal (the Interdictions, and the Barnacles) - I did however see a few vids of CMDRs pursuing and firing upon departing ships; even some of people who got in the way of something a ship was doing to a Barnacle, and called it an attack, but was it?
Other events, Aftermath scenes of destroyed ships (no sign of anyone actually doing the destroying) and a Thargoid leaving, or just the remnants of a battle. Lots of "obviously Thargoid" weapon destruction - green goo, green mist, etc.
Speculation:
1. What if the witnessed events of destruction with a ship leaving was in fact seeing a Thargoid leaving a scene after also finding a distress signal or unknown signal?
2. The tech we might have gotten from Thargoid - what if all the Engineers are masters of reverse-engineering, and all these ranked up modules a result of that work? It might even explain why this same tech may not be effective against the Thargoid - perhaps?
4. The coded repeating signal at the latest site simply says "Thargoids Return" - a very vague message - It could be a warning, a confirmation, maybe even a request?
All incident sites simply shows aftermath evidence of something that wreaked this destruction. That's all it shows. Maybe there are other clues there that are yet to be found giving more insight into what actually did happen.
3. Deeper speculation still: What if the flurry of abandoned, destroyed, sabotaged generation ships etc was the work of an organisation up to some nefarious skullduggery and who are in turn setting up Thargoids?
Other side of that same coin: What if that same organisation has been working with the Thargoids surreptitiously all these years?
I don't know if I'm over thinking things (I probably am lol), and also missing the most obvious things that are actual confirmation of Thargoid aggression - but I'm sure having fun mulling over the possibilities. with the occasional "ooo oo ooo! What if... ?" additional thought.
Hopefully my speculations may trigger some further speculation, or even a different perspective to look at all this, leading to deeper investigations.