As a referee, I have very mixed emotions about VAR.
For offside, yes, no problem. That's 100% an objective decision and we all want it correct. In practice, I think the tech is still not quite up to the task as you must sync the instant in time the ball is touched (not when it leave contact but when contact is first made) by the player making the touch with a body part that can legally play the ball by the player in an OS position. And all of that is subject to the frame rate limitation in the video.
For a goal, that's not VAR that goal line tech and its not really reviewed. Its basically the tennis Hawkeye line system and it immediately vibrates a band on the refs wrist when the whole ball crosses the whole line. There's no human in the loop.
In theory nonsense off the ball (VC in particular) should be a good idea. In practice I don't think that's always being done. The Mens WC in particular they just flat ignored it. Nikolas Otamenti committed VC twice. Both times in a dead ball situation, he kicked a ball in someone's face. It was blatant, it was with force and it was on purpose. Its 100% violent conduct. The CR either saw it and ignored it or didn't see it. It was caught on video for the entire world to see and the VAR could not possibly have missed it. And yet somehow he was never punished. You cannot explain that other than they (FIFA) has told referees including VAR that they should not use it for its intended purpose. If you aren't going to use it, why have it?
The handling stuff you see now is beyond dumb. Handing is really a subjective call. And VAR is being used here to rereferee the match (mostly). Some are missed, but most of this is the referee and their training saying "no PK" and the VAR is rerefereeing the match in a booth. In the WC last year one referee made the call of no PK, he got the buzz to look at it (and the VAR is basically saying you committed a "clear and obvious error"), he looked and decided he was right and VAR was wrong and went with his call. He got sent home. So the message was ignore VAR and you are done. That's rereferring a match.
Now in the U20 WC we are seeing VAR catch GKs off their line in very ticky tacky ways.on PK attempts. And they are getting carded for it.
Its gone way too far.
Mark my words. Theres going to a very big controversy in the WWC all because of VAR. The women who are reffing the matches basically have never used it and are struggling. Witness the incredible delays already with ARs not flagging offside. They are also calling handling very tight with it. And the new Law changes for GKs on PK attempts are going to cause issues. Something really bad is going to happen because of VAR. I would not be shocked to see a GK get carded out of a game because VAR says they cheated on a PK attempt. I hope not. Put I'm not holding my breath.