I was using ChatGPT only as an example - I don’t think that making a chatbot AI is their focus, so it’s understandable that they are not as good at it - plus, I’d guess that making a coherent text is a lot harder than deciding what kind of video or posts to put in someones feed.
And that AI, the one that takes users data as input and outputs what to show him in his feed to keep him glued to Facebook for as much as possible, I’m almost sure is one of the best ML we have on the world right now - simply because of the user base and time it has to learn on, and the sheer amount of data Meta has about users. But that’s also something that will never get public, naturally.