You're talking about 2 of the most brilliant minds in the universe.
Thanos is always prepared and Doom is, well Doom.
Thanos was surprised by Warrior Madness Thor and stopped him as soon as he wanted to.
If he had his devices, like the post says, the heroes have no chance.
Again, that was not stipulated in the original post. Nothing about prep time, and nothing about them having access to various different devices was allowed for. If I remember correctly, when Thanos fought Warrior Madness Thor, he had to leave the battle to go get his force field gun to neutralize Thor. Who says that will be possible if WBH punches them out of existence? Or if Dr. Strange allows them to? Or if Ghost Rider's stare works? That's why I said it depends who gets off the first shots in those instances. If villains can take out Hulk before he goes WBH they win. If not, the world gets destroyed but heroes win.