Many comments are ignoring the most important aspect. The decline is almost all among men not women: > Using a slightly different age range and time frame, Ueda et al. (2020) found that the percentage of sexually inactive men ages 18 to 24 increased from 18.9 percent in 2000–2002 to 30.9 percent in 2016–2018, and the percentage of sexually inactive young women increased from 15.1 percent to 19.1 percent over the same…
It's probably more than that. You don't have to be some 6ft tall hunk to land a woman. It definitely helps but it isn't required. What is required is that you try and don't get discouraged. It's a lot easier to stay home, play video games, and watch porn than it is to date. Plus, successful dating reduces time for video games.
This is true, but what you do need is access to women so that you can learn what they want.
If those women have a low incentive to spend time with less physically (or financially) attractive men, it’s going to be hard for the less attractive ones to develop the necessary capacities.