Well, an AR can't "call" any offenses at all. The AR can only recommend the R makes the call. But that doesn't necessarily shift the concept here, as one can ask why the VAR can't recommend a call without the R seeing it. I think there are a few answers there. First, the VAR does recommend without the R's review on all "objective" calls. For judgment calls, we are often talking about a call that the R saw but made a different judgment from the VAR on what he saw. So if we are keeping the concept that the R makes all calls, then we would be asking the R to simply accept that he was completely wrong on what he saw, even though he was confident enough to make a call (or no call). And if we don't let the R have final say, that is a very deep change to many decades of the concept that the man in the middle owns every decision. And having VAR make the decisions alone, without the R, gives the R less control on the pitch, as the "eye in the sky" is "really" making all of the important decisions. And we couple that with the fact that the R is, in general, a more senior ref, so we'd be letting a more junior ref overrule the more experienced ref on the field. So I'm not sold on eliminating OFRs on subjective calls. (Though I could see a bit more flexibility where the R would have more discretion as to whether to go to the monitor or accept the VAR recommendation depending context and why the R did or did not make the call. But I think that is probably an evolution issue once Rs, VARs, teams, and fans are more linked in to the process.)
That said, the process can definitely be run in better and worse ways. I do think that MLS has been a leader in developing and implementing efficient processes on OFRs, including the images shown to the R. The MLS VAR is typically telling the R as he runs over what the first image is, and showing the best image(s) for the particular decision being reviewed. The MLS Rs are also typically good at owning the OFR and telling the VAR if there is another view they need to see to confirm the decision (and the skilled VARs are typically ready to show those other images, as they've already vetted the other images). But at the end of the day, a lot of this is about practice--it takes experience for the VAR to be efficient and for the R to drive efficiency. Just like ARs having to adjust to when to delay (and not delay) OS flags, VARs and Rs need to learn to do the OFR effectively. The WC refs and VARs haven't done tons of VAR FIFA games. So much of what we see is an indication of the skills that they have learned (or not learned) in their domestic leagues. And the quality of implementation in the domestic leagues varies wildly.
