A major reason why people aren't having sex anymore is because 40% of the population is obese
And that number is just the people classified as "obese". If you expand it to include any weight range deemed unhealthy by doctors, then 75% of Americans are classed as "overweight".
I'm sorry but I just can't get aroused by huge people. They hold zero sexual appeal for me. If I had to choose between a 220lb 5'3" person, and some sexy pictures + my hand, I'd choose the sexy pictures everyday. And I know I am not the only one who feels this way, and yet this is overwhelmingly the body type I am the most surrounded by, here in the Deep South.
You want to fix the "gen Z are not having sex" problem, a huge step in the right direction would be addressing the health crisis affecting the country right now. As much as we preach "you can look good and be healthy at any size!" it's just not true, and you can't magically change what people find attractive on a visceral level.
Also, I know the reasons are multifactorial and I know that it also involves a lack of financial independence, lack of social skills due to social media addiction, jobs being too unstable or demanding, etc. But a lot of these other reasons never actually come into play if the person you're looking at doesn't even appeal to you sexually. You would never flirt with them for that reason alone, the same way I wouldn't flirt with my male coworkers because I am straight.