Your feed keeps serving what you already like. Learning means going after what it never shows you.

A recommendation system is built to predict what you will stay for, which means it narrows towards whatever you have already approved. Nothing malicious is needed for that to shrink your world; agreement is simply the most reliable way to hold attention. What you never see is invisible by definition, so the narrowing does not feel like narrowing.

Go and fetch something deliberately this week instead of waiting to be served. A library shelf, a suggestion from somebody older, a subject you have no opinion about. Choosing badly on purpose beats not choosing.