Software isn't fungible and right now today you have the ability to install facebook with app store restrictions on iOS and without on Android. If FB pulls from the app store that choice is taken away.
You have a third choice: don't install facebook at all.
No, you can't. You can have some protections against the most egregious overreaches, but if you're concerned about privacy you shouldn't be on Facebook, ever, on any platform.
Aside from that, there's no way Facebook will remove themselves from the app store. Apple isn't going to make sideloading easy enough for the average Facebook user.
No, you can't.
And if you could, the protections aren't that good.
And if they were, it's not going to happen anyway.
And if it does, that's Apple's fault for making it too easy.
And even so, you deserve it anyway for using Facebook.
Facebook has 2.95 billion MAUs and 73% of the entire US population actively use it, 93% of businesses are on it -- "just don't use Facebook" is a woefully out of touch take. And this is only Facebook and doesn't include IG and WhatsApp. Meta is 4/4 of the most downloaded apps.
It's worked for me so far, and we're way past peak Facebook, so I don't see myself needing to use it in the future. Businesses still have phone numbers, and none of my friends or family are active on any Meta platform. I really don't think it's the pillar of society that you seem to think it is.
You can't solve a behavior problem with OS controls. It's not about what bits on the device are readable it's about what happens with the identity information shared with 3rd parties.