Then you have a different problem.
Suppose you have some content that depicts healthy and loving relationships, but is also sexually explicit. The prudes are going to want that inside the porn filter along with the rest of it, even though it's something that does the opposite of what you're concerned about.
Meanwhile, insert "watch it for the plot" joke, because we all know that kind of content gets produced when the goal is to appeal to the prurient interest without allocating a lot of budget to writers. But that's actually the problem. Age gates and things are friction. Suppose you want to create something good that appeals to a mass audience because it's thoughtful, but it's also sexually explicit. As soon as you put it behind the wall you lose the large majority of the audience, not because they're minors but because they're adults not willing to swipe their ID in order to watch "porn", whether out of the assumption that anything with that tag on the gate is inherently immoral or concern that someone else would assume that if anyone found out they were watching it.
And then the wholesome and salutary stuff doesn't get produced. You'll notice that such content is uncommon, because it's effectively banned in most of the places with even moderate production values. You can't put it on broadcast TV, "porn" is banned wholesale on YouTube, corporations the likes of Disney would generally be skittish about producing it etc. You'll occasionally get something like that on HBO or Netflix but even then the incentive to produce it is lower because they wouldn't be able to license it to as many other places.
Which means the main place it gets created is in places like the old Tumblr before the prudes killed it. But killing Tumblr doesn't get rid of porn, it just lowers the quality of it, where "lower quality" is more rather than less misogynistic and insalubrious.