Much of this data can still be obtained through scraping without the API. Depending on official APIs for data collection has never been a great idea, as they are often governed by very low rate limits etc. The Facebook API has been useless for social apps since the 2014 changes anyway, so they have made something that was already useless even more useless. Hopefully everyone here saw the writing on the wall in 2014 and isn’t relying on the Facebook API for business processes or revenue in 2018.
They shut down what was used by the company which I forgot the name to harvest the data that was used by Cambridge Analytica.
I don't have the details, but it was mainly around app having access to a lot of your friends data as soon as you would give the app access to your Facebook account, without any concent from your friends
