Good. Don't use them. Do you use every single feature of your phone? Of course not. There are probably features you don't even know about.
So don't use them. The mere presence of the feature doesn't obligate you to use it.
Why the hell should Facebook comply with Apple’s every whim and wish, if they could just publish on a different store with less stringent privacy rules, and force you to download it that way? “You want Facebook? Go to Settings -> Privacy, then uncheck the bla bla bla box, and install Fb Store. Then...”. Yeah, no, that’s my worst nightmare.
Seriously, how do you people not get this?
There's no reason Apple can't enforce the same privacy options OS wide, even for sideloaded apps.
Of course they don't want to, they would lose their 30% cut. But if they are forced to allow 3rd party app stores they would have to, if they wanted to continue their privacy focused marketing.