It may have reduced error rates by getting those millimeter offside decision "correct" (although frame rates and movement speed of players puts many such decision in doubt), and it has been used to "correctly" disallow goals in situations where the ball touches the hand of an attacker (the guide lines for handball is every bit as fucking stupid as VAR). It might be a bit more precise for such decisions than the onfield referee.
But I have to ask: Who calculates the error rates? We keep seeing experts disagree on many situations. What is a correct decision, what is not? Is it perhaps possible that those who find that the error rate has decreased is biased and wants VAR? And does the error rate evaluation take into account all decisions made, including the ones that VAR does not evaluate? It has appeared that onfield referees have become more reluctant to make calls. I believe a lot of errors are made where the onfield refs does not make a call and VAR does not intervene at the moment.
Even if fewer errors are made, the cost is disproportionate to the gain. The cost includes the time it takes to wait for decisions to be made, the euphoria-killing fear that the goal may be turned down by VAR when a team gets the ball into the opponents net, the added layer of frustration and anger when decisions are erroneous, as they are way too often and too clearly, after review by VAR, the frustration and confusion when important calls for some ridiculous reason (often defined - stupidly - in the guide lines for VAR) are ignored by VAR (like the foul on Moura prior to the "handball" or the elbow in the face of Son that should have been a second yellow), and more.
The VAR system is completely moronic and damaging to football. As are many changes in guide lines for rules such as the handball rule. The people put in charge of defining and enforcing the rules of the game are clearly a bunch of clueless cunts who do not get the game of football, who are more focused on trying to solve the impossible Sisyphus task of removing the error-potential of the rules and guidelines for enforcement of the rules than ensuring tha the rules and guidelines are such that football is football.
One example is the handball rule: In an attempt to reduced the consequences, or whatever, of a rule that it is hard to enforce correctly, they keep changing what is a punishable handball. It went from active use of arm to deliberately interfere with the ball, to a ridiculous regulation including "natural position" which was hard to get right (costing us a CL final), to an even more ridiculous regulation now which says that if a defender is hit in the hand it is not handball but if an attacker for any reason whatsoever is in contact with the ball with his hand prior to a goal the goal should be disallowed. It is unfathomably ridiculous.
Another example is a suggestion to a change to the offside rule made by a group lead by Wenger, if I am not mistaken. They were trying to solve the problem of the controversial millimeter-decisions and VAR still pictures measuring armpit positions. Their solution, which according to them was to solve the entire thing and fix the problem, was that the the attacker fully had to be in an offside position, not just a part of his body with which he could score a goal. It is ridiculous beyond belief. Not only would that lead to similar millimeter-based decision, it would also greatly change the offside rule and allow forwards a greater advantage.
VAR is shit. And so are the ones regulating the rules of the game.