The biggest flaw for me is how do VAR know exactly when to freeze frame on the pass. There's no way they can pinpoint the exact moment that the ball leaves the boot.
On such marginal calls like the one today they could be pausing the action a fraction of a second later and in a different game pausing it a fraction of a second earlier, and that could be the difference between the player being offside or not.
I'm all for clear offside goals being disallowed but there's going to be a lot of inconsistency on marginal calls.