This is such a simple thing that they've fucked up so royally.
What is the purpose of the offside law?
To ensure that players cannot gain an unfair advantage by not moving their positioning with the flow of the game but instead staying stationary (i.e. goalhanging).
Did Raheem Sterling have an unfair advantage due to one part of his shoulder being 0.0001mm in front of the last defender?
No. There was no advantage to Sterling in a football context by that extremely small gap. If you would have moved him back to before the offside line then the outcome would have been exactly the same, frame for frame.
Does VAR actually help enforce the point of the rules of the game?
No.
Are the people who say "you're either offside or you're not" completely missing the point?
Yes. Unless you're advocating getting an electron microscope out then the idea of absolute objective positioning is pointless, and even then you've have to measure it without somehow changing the position which breaks the laws of quantum physics. Absolute positioning doesn't exist in any meaningful context. It's not about atomic sized positioning, it's about whether or not the player gained an advantage due to his positioning.
VAR should be in the game. It should be used after every goal. But the game should continue as if there's no decision to be made and then if one needs to be made, call it back. Any decision in which you can legitimately talk about human error of the operator or the concept of absolute positioning in quantum fucking physics should not be tested with VAR.