First of all, I agree that he was (almost certainly) offside and I'm obviously delighted. But the issue is that once you move something from a human to a computer (although that's not strictly true in this instance) then tolerance for any perceived imperfection is greatly reduced. It can't just be better than a lino 3 yards behind the play, which it currently is, it has go be essentially infallible and very quick. It's like self-driving cars -- they don't just have to be as good as the average driver, they need to be much better than any human driver we could conceive of before the general public is very comfortable with them.