I was just making a joke. The plot fails because it's a film about a bunch of people with magical powers not based in any way in reality who can't take somebodies glove off. Any criticism past that is stupid. This is a villain who watched his world die, try to accomplish something insane. That's it. He's not a round table of philosophers or 30 Caf members bouncing ideas off of each other, nor did he go to university to develop his critical thinking skills prior to hatching his plan. He got an idea and ran with it, like half the UK public did with Brexit and like half the US public did with Trump for also stupid reasons. People make stupid decisions that don't make sense every single day. As someone said above, if you can accept a premise of Norse Gods, magic stones that alter time and reality itself, flying sorcerers and technology so advanced you can pretty much make whatever you want happen just by thinking it i.e Iron Man's new suit and a guy who can climb on walls because he got bitten by a spider then you can forgive an evil person who's plan is flawed. I don't know where this requirement came from that villains must have totally logical, sensible plans that are infallible. I don't remember that ever being the case in any film I've seen with a villain in it. Or if someone could name an outlier, it would probably be exactly that.
If Thanos said 'half the universe there or thereabouts' would that make it okay? Does he have to give Neil de Grasse Tyson levels of mathematical accuracy for the plot to be okay? Of 7 billion people on Earth, how many people do you think are on planes that crashed? not even 1%, barely event a dent so you can to the normal person just use the phrase 'half the population'. Nobody cares about these distinctions, and they're making these movies for the millions of people that will go and watch them, not the hundreds of people that pick apart semantics. For all you know someone said in Marvel 'what about the guys on planes' and everyone else said 'lol are you joking, why would a mad titan give two shits about a thousands people on planes when wiping out billions?' and then they said 'ah yeah good point, that is a bit silly tbh'.