The Leftovers was incredible. Absolutely my favorite television show of all time. If you’ve lost someone close to you, you might even appreciate it more. Woefully dark television.
That said, Leftovers was 2% of the population that vanished. Not enough to ruin a society but still enough to have an immediate impact of the psyche of (at the very least) someone you directly know and care for. So if not your immediate family, a friend or family member.
Infinity War, on the other hand, the world would have completely collapsed. Every society would crumble. Every currency would inflate to worthless. Suicides and depression would be so large it would wipe out hundreds of thousands (or more) alone. Not to mention the crime, violence, famine and disease would wipe out millions more.
The short of it is- a show would be basically the walking dead without zombies. The fact that the world stayed relatively the same, just less 50% of the population isn’t even unrealistic and improbable, it’s impossible. But I get why they did it. Hah