That’s naive. If you have a Facebook account they know every website you go to that has affiliate advertisement or a like button on it. I’m sure they also broker data from other companies and mine it from public sources. My uninformed guess is that < 10% of the data Facebook has on any given person comes from their actual interaction with Facebook.com.

Unless you are using Facebook containers in Firefox, or even self-destructing VMs to access it (as I do).

Or just use an ad-blocker extension like uBlock Origin, which blocks Facebook's trackers (and Google's, and others).