The headline and intro led me to believe this is a dip -- e.g. that young people 5 or 10 or 20 years ago liked the amount of sex, but young people today don't.
But that's not what the survey shows. All it shows is that people aged 13-24 today want less of it.
It may very well be the case that this isn't anything specific to Gen Z at this age, and that this was equally the case of 13-24 year olds 20 and 30 years ago. TV and film has been pretty sexualized for a long time. There is zero evidence in this study to indicate anything new.