Ideally, parents should be able to sit down and talk to their children about sex and love bit by bit. You don't overload them with details (especially when they're small because they're too young), but you also don't completely censor them or lie if and when they ask questions.
Ideally, schools and media shouldn't have to be the one teaching kids sex or putting restrictions on what they see.
Realistically, it's not that easy.
As @Merle hinted at -- there are a large number of parents who don't ease into the sex and love talk it with their children. They either shut it out, discourage them in a way that makes the topic shameful, or they don't teach their children that it's something they should do when they're older and those same children end up doing something no child should be doing.
The last one I've seen growing up. I went to grade school with children who tried mimicking sexual acts because that's what they saw around their parents or guardians. And at the same time, I went to high school with children who were shamed into not masturbating and were completely in the dark on consent and telling people "no" if they were uncomfortable.
Realistically, some people just don't know how to teach children about sex and love. I'd also argue some people just shouldn't be having kids in the first place, but that's another topic.
I'm another advocate of "letting kids be kids". While my father and aunt did give hints and answered my questions when I was small, it was never full on details, and it was insisted it wasn't something I should be worried about. However, when I became more mature, my folks sat me down and began to elaborate. I didn't find out about the details of sex until I was 10,11 years old, and it was introduced to me when my aunt sat me down to talk about menstruation.
It was gradual and more close to when I was pre-teen, teenager. I was able to still be a child and think like one but also learn to understand the importance of sex, love, and consent when my folks thought I was old enough to understand that.
Now, as a creator, I won't censor myself. If I feel I need to talk about a topic or show an explicit sexual scene, I will do so. But I still have a duty to put up warnings and some blockades because I know there are parents out there who aren't doing their duty. So I can see why there's a censorship -- if a minor sees my work, despite me putting up a blockade, it turns the responsibility on the parent, not me.
It's because realistically, some parents aren't talking to their kids that media has to step in and do it for them. Which is BS, it is. But if we want to reduce that censorship, we kinda have to turn our attention to how people talk to their children when it comes to sex.
But that's only half the battle.