All Thanos has to do is implement a one child policy. This way he wont directly kill anyone. He just cut their bloodlines short, which is in the long run killing a person off, but it is much easier for the whole universe to swallow. Thanos will not have to fight so much now.
He has the infinity gauntlet, so he can snap his fingers and wish for every being in the universe to lose their reproductive capabilities after one child. Like as soon as a man cums, he automatically get vasectomized. Once female gets pregnant, her ovaries produce no more eggs.
This method is not so finite either. People will actually get the chance to see what it is like. In their minds they have a choice. They will think, if I want more kids down the road we can always vote to reverse it.
Its really that simply. Thanos is not as smart as people make him out to be. I am smarter. In fact, I even have a plan to beat Thanos using Dormammu. So I am smarter than all the MCU.