The thing I really don't love about ATProto is its decision, or that of its dominant implementation to enforce a schema ("lexicon") on content, limiting interoperation between disparate software. This violates the Old Internet idea of software being liberal about what it accepts.
For a concrete example, I tagged a Lemmy community in a Mastodon post today. Lemmy is Reddit-like and Mastodon is Twitter-like, but it displays reasonable on Lemmy using the first line of the post as a title and expanding to the attached image when clicked in the default Lemmy UI. I can also post a long-form article on Wordpress (with a plugin) and have it show up in Mastodon even though it has a short character limit by default.
ActivityPub by contrast lacks such social coordination and many apps are reusing the same schema for very different concepts, leading to its own form of over-complexity
For a concrete example, I tagged a Lemmy community in a Mastodon post today. Lemmy is Reddit-like and Mastodon is Twitter-like, but it displays reasonable on Lemmy using the first line of the post as a title and expanding to the attached image when clicked in the default Lemmy UI. I can also post a long-form article on Wordpress (with a plugin) and have it show up in Mastodon even though it has a short character limit by default.