As others have said, this won't be the end of humanity. But the western Roman Empire underwent a similar population collapse, with survivors huddled in cities with 5-10% of their peak population as things went to ruin around them before the barbarians swept in virtually unopposed. It was the end of civilization.
Seems like we are going through the same thing again due to AI and the conquest of the West by Islamists.
It’s just that with each ejaculation, what is it, I forget, 500 million sperm or something. So 50% would still be 250 million which is still amazing so maybe we can’t see the effects quite yet. But if they keep dropping and trending towards there really could be nothing worse.