Goings backwards in time will never be invented. Proof? On D-Day there are no stands full of spectators or drones in the sky recording everything. Q.E.D
Or we live in the timeline that leads to the invention of time travel, not the one the time travellers are visiting. Maybe the universe allows time travel but it always creates a divergent timeline when you use it.
Does not hold. Time travel might be invented after the cloaking device!
no [...] drones in the sky recording everything.
Are you sure about that?
https://en.wikipedia.org/wiki/Foo_fighter