The Open Graph Protocol was thrown over the wall by Facebook and promptly abandoned. It’s an atrocious spec, a good chunk of what it did (and most of what people actually wanted from it) was already unnecessary (og:description, for example, is stupid), its data model makes several woefully bad choices, it’s firmly based around Facebook’s interests (especially pictures!), it’s built on standards that were already looking like they were failing and are definitely long abandoned now, and I don’t think I’ve seen a single page implementing OGP tags correctly in the last five years and I’m not confident that a strictly correct reader implementation even exists (the specific matter I have in mind pertains to the prefix attribute). Also a bunch of key URLs have been 404ing for many years now.