AO3 is funded by a deep-pockets not-for-profit. They do very aggressive fundraising as well, which allows them to roll out new code as needed. That’s my staff member response.
Now for my personal response as a writer… AO3 fosters a great deal of confusion when it comes to moderation. The Terms of Service is obscure, and unevenly applied. I ran into an issue there with utterly baffling moderation that favored a cybertroll over the author who was targeted. While it was not aimed at me, it had the effect of thoroughly discouraging the author who was targeted, and I filed a formal protest with AO3’s legal team over the bizarre and inexplicable use of the Terms of Service to victim-shame and gaslight someone who is a singularly talented writer in favor of protecting the delicate sensibilities of a trollish brat who spammed a review over and over, deleting and reposting it to create a near-constant barrage of email notifications.
Yes, there are some lovely features there, like kudos and word counts. There is also a built-in download feature, which lets anyone download your work, in a variety of formats. Personally, I find that deeply objectionable, but as a “creator” I do not have the option to opt out of allowing my work to be downloaded. Granted, AO3 is not geared for works of original fiction, but I would still like creative control over my fan fiction. That’s a me issue, apparently.
I also hate, with a deep and abiding passion, the free-for-all tagging there. Without some standardization, it’s impossible for tags to have any actual meaning as warnings, and no one enforces the use of trigger tags. I don’t read Minor1 fiction for enjoyment, as an example. I loath being blindsided by that content as a reader. I also don’t believe there is any such thing as dubious consent. It’s yes or it’s non-consensual, otherwise known as rape. I’m too damned old and cranky to play word games about that issue.
That’s my take on AO3, and sorry for the rant!