Landmines are worse, because they don't even know, the war has ended.
This is the terror element. People will have to worry about getting blown up anytime, anywhere. That's why we keep making weapons with more range and better targeting, because waiting for the target to come to the weapon just wasn't horrific or effective enough.
Sure, landmines are really bad but we're inching closer to things that surpass landmine horrors in every way and makes them seem like the lesser evil. Because if there's one thing that's bad, it's taking an already bad thing and augmenting it. And that should really scare you.
If someone really wants a hit on joe random citizen, why would they choose one of these drones over the traditional method? Much harder for a weaponized drone hit to look accidental.
> why would they choose one of these drones over the traditional method
Why does anyone use automation or AI for anything? To have dozens or even hundreds of drones constantly in the air with close to no supervision from drone operators. When you're going after an enemy false positives and collateral damage matter very little, if at all.
> Much harder for a weaponized drone hit to look accidental
Nobody bothers making deaths look accidental in the places these drones will be used. If reality showed anything it's that they barely bother to argue when they bomb schools and hospitals beyond the boilerplate "we're fighting terrorism".
This kind of tech makes a bad situation even worse for many people in some parts of the world. But you'll start worrying about it only if/when someone decides to use it somewhere in a civilized country, closer to home. I'm sure so many people will suddenly find plenty of arguments against the autonomous killing machines then.
Drones have been used quite successfully for many decades now and clearly haven't developed any countermeasures for what most of their targets are concerned, "quickly" or otherwise. This is why we still read about drones bombing people out of existence, whether the correct target or not.
An autonomous drone just outsources the usual killing from the human operator to a script, making it even more likely to make a mistake and also apply the desired effect: terror.