The only reason to use technology is if we're going to end up getting significantly more correct decisions. I agree with you about offsides and handballs that lead to goals - these are matter of fact decisions and even if the technology is not 100% accurate, it'll be far more accurate than the officials eyesight and the end result will be getting almost all these decisions correct.
Now I'd have no problem with VAR not being used for subjective decisions but the issues we face really aren't as difficult to overcome as you make out. VAR is being controlled by a qualified official and despite what we sometimes might think, they'll all know the laws of the game. For 99% of incidents a professional ref should be able to look at a handful of replays and be able to reach a decision that will be the same as any other ref. And that 1% of incidents, that after those replays they can't make a confident decision on, they stick with the on field decision. The end result will be far more correct deicions being made. Unfortunately not upsetting the on-field ref is more important than making correct decisions though so as long as we can understand why they made the wrong decision, we'll stay with that wrong decision.