The problem is that offside is a matter of fact, not opinion.
No matter how small the margin, offside is offside.
It doesn't matter how much you tweak the lines, or the rules/guidelines there will still be marginal decisions and offside will still be offside.
I prefer the old system where if you have a doubt then you glance at the linesman (sorry assistant referee) and if the flag's down it's a goal.
Of course mistakes happen, but mistakes are a part of the game. Without players making mistakes the game would be boring.
Why should officials be exempt?
Except that it isn't. There have always been 3 possible states of existence for the attacker. In front of the defender, benind the defender, or level with the defender. "Level2 is not, and never has been, and is not intended to be an infintitely small distance. Remember 1990 when they changed the law to say level was onside instead of offside? They expilicitly said it was to give the attacker an advantage and to encourage more goals. Nowadays they would have you believe that they actually meant an advantage of a millionth of an inch. They did not mean that. "Level" means, in practice, too close to call with the naked eye.
And even if the law as it stands does mean that level is to be judged to the millionth of an inch, then why not change it back to the 1990 law? After all, suppose the VAR offside interpretation had been put to the powers-that be honestly. It would go somethnig like this.
"Boss - remember how 30 years ago they changed the law to allow more goals by saying that level was onside? Well - I've found a way to change it back half way, so that half those extra goals are disallowed. What we have to do is introduce technology to judge offside by the millimetre. We will have to have long delays of up to five munites during the game, and it will become impossible to celebrate goals wholeheartedly because we won't know until kick-off whether the goal has been given, and the linesman will have to wave play on when he is intending to give offside later, but we will be able to disallow all those goals,"
And hopefully, the boss would have asked why disallowing goals is a good ambition, and tell him to sling his hook.
If they must have VAR for offside, then give the VAR man a still photo and see if he can tell the linesman is wrong. If 5 seconds later he is still looking, then the linesman is right.