So when it's all said and done, I do not expect practical levels of actual isolation to be that great.
The data doesn't support the suggestion that this is happening on any mass scale. When Apple made app tracking opt-in rather than opt-out in iOS 14 ("App Tracking Transparency"), 80-90% of users refused to give consent.
It does happen more when users are tricked (dare I say unlawfully defrauded?) into accepting, such as when installing Windows, when launching Edge for the first time, etc. This is why externally-imposed sandboxing is a superior model to Zuck's pinky promises.
But when the choice is between using the app with such spyware in it, or not using it at all, people do accept the outrageous permissions the spyware needs.