There is a difference between judgment calls and line decisions. With line decisions you are always going to get calls so close that with the naked eye you would be guessing. John Stones cleared one off the line that was millimetres from being a goal, but was correctly judged not to be a goal using goal line technology. There can’t really be any argument about using technology in that situation in my view.
I remember a few years ago the offside rule was that there had to be ‘daylight’ between the attacker and the last defender. That would still produce cases where a player is on or offside by millimetres. But it’s better to get more calls right by using technology than it is to leave more to the officials guessing.
With subjective calls, like you say there is a strong argument for reserving the use of VAR for really outrageous cases, like the Henry handball against France. What that means, though, is you are back to square one because a penalty is far more likely to be given at the swamp if the team claiming the penalty plays in red. So you are swapping one set of subjective decisions for another.
To my mind the biggest problem with VAR is the lack of transparency. What’s the problem with hearing the discussion between the VAR official and the ref? Last year if we had heard the discussion between Oliver and the VAR team when TAA hand balled it and they went up the other end and scored that might have avoided a lot of suspicion.
There is no perfect solution but hearing the discussion would at least explain why certain decisions are given.