But there are also other requirements in section 201 for a "covered platform", which advertising-funded sites that aren't "social media" most likely don't meet. For example, a typical personal blog, even if it shows ads, doesn't meet subsection (C), because its primary purpose is not to share user-generated content (e.g., comments by readers)--it's to share the blog author's content.
(HN itself doesn't meet at least one other requirement besides subsection (E): subsection (D), "Uses a design feature to promote user engagement on the platform".)
True, but in practice, the vast majority of advertising-funded sites use targeted advertising, because they use standard ad networks. There are very few ads networks that don’t do targeted ads.
You're assuming that platforms that tried age verification in order to show people targeted ads would lose enough users to make that business model no longer viable. While I would fervently like to believe that's true, I'm not so sure it is. I think there might well be enough people who will hand over their personal identifying info without a second thought in order to continue to use targeted ad-supported platforms, to keep them in business. I hope I'm wrong.
I don't think it'll come down to people being too principled to participate. I think I'll come down to them being too lazy to bother completing the auth ritual.
(HN itself doesn't meet at least one other requirement besides subsection (E): subsection (D), "Uses a design feature to promote user engagement on the platform".)