It’s none of those things, sperm counts have been falling all across the world for decades.
Takes a healthy couple in early 20’s an average of 6 months to conceive and much longer by age 35.
It’s more likely to be something really stupid like the rising polyester content of male underwear. https://nostr.build/i/e8ef886a7d2da4ae165b7fedd21e5350054776f2f7cebf80e98930790ee6bc90.webp