Both are creative writing sites with large/primary focuses on fanfiction. AO3 (Archive Of Our Own) allows for works depicting rape, incest, and pedophilia. IIRC Wattpad never did.
part of the impetus for creating ao3 was a series of content purges intended to hit bad evil content also hitting, for instance, support groups for survivors, and g rated content if it was also gay.
its code is open source so i genuinely think people with their own ideas about moderation should take advantage of that or anything else (wordpress?) to make an archive. if there are good stories on it, i'll visit. There should be more archives in general.
This is going to be a controversial opinion, but I really wish we had gatekept AO3 from the portion of the Twitter fandom crowd that keeps getting all the manga/anime/game/tv piracy sites taken down by blasting it all on social media.
Not everything has to be for everyone, and also if you don't know what "Dead Dove: Do Not Eat" is or don't know how to Google it...maybe the website isn't for you.
I don't know shit about either of the sites other than that there's fanfic there, but my reading of the post is the other way around. I'm pretty sure they're saying that:
Wattpad enforced stricter standards than AO3
Presumably Wattpad's userbase diminished as a result
Now that Wattpad has died or something, the people that supported Wattpad's stricter standards have moved to AO3
Those people now demand that AO3 enforced Wattpad's standards
To be honest, one of my sources of confusion is that the second paragraph suggests Wattpad users are trying to make AO3 allow their type of content, but the third paragraph/second post implies AO3 is too permissive for Wattpad users. The two messages seem opposite each other in what they get across.
One possibility that had occured to me was that AO3 is too permissive for Wattpad users in terms of classification, but that AO3 was a fanfiction site and Wattpad maybe has a mix of fanfiction and OC and that they were annoyed at the OC not being allowed. That would seem to reconcile the mixed messages. But honestly there's nowhere near the evidence from these posts and what little I already knew about the sites to be even remotely confident in that conclusion.