Apple's latest software update requires companies and app developers to share details on what user-information is collected when a user uses their apps; sort of a "nutrition label", but for your data. They aren't necessarily stopping this collection of data; they are simply giving you the chance to be aware.
It's well documented that Facebook is notorious for collecting a lot of data (which would explain how you always happen to see very personalised advertisements). Though Facebook tried fighting Apple's privacy requirements, we're now able to see more clearly how much information is actually being collected.
You can take a look at it yourself-- go to your Apple App Store, select Facebook Messenger, and scroll down till you see App Privacy; you'll see how much information is being collected without you being aware of it.
P.S. This includes everything from your health data, purchase history, location, contacts, browser history, financial information, and... well, pretty much everything.
P.S. After backlash, and seeing how they've lost millions of users, WhatsApp has postponed this by a couple more months.