Thanos's logic is flawed
Thanos snaps his fingers and halves the population of the known universe by half....but what would that accomplish? The world's population is 7.6 billion people, so if he halves it it'll be 3.8 billion people, what the population was roughly in 1967...so assuming Infinity War occurred in present day the earth's population would be back to its present number of 7.6 billion in roughly 50 years and presenting the same problems again with overpopulation and low resources.
Had Thanos used proper logic he would have lowered it further, dropping it by 50% only puts a band aid on an open wound.