Indeed, if Lolita was published today, it would probably be under the original fiction tag. Now tell me with a straight face that you wouldn't purge it together with the porn in that tag if you were an AO3 mod.

Also, works can also include "rape aftermath", especially in a ship context, and still be written for the purpose of smut.

"Can" is not the same as "is". I do not deny that there are works posted on AO3 which cross the line of good taste. My argument is that those works are neither popular nor more common than ones which don't, or which may contain some problematic elements, but those elements are offset by the literary value of the work (what's your opinion on Game of Thrones winning multiple awards? What's your opinion on the multiple incest storylines in Tolkien's Silmarillion? How about the Greek mythology? If those works of fiction had their start today on AO3, their authors would've been doxxed and chased off platform).

My problem with you is that you artificially narrow your lens for fanfiction so that it shows only the irredeemable pwps, while ignoring the several times more vast number of stories which are either completok, or exist in the vast grey area of morality. That's an intellectually dishonest take.