Shouldn’t the money be used more efficiently for society’s benefit or not concentrated by the share holders? Share holders will only further their own interests and not society’s interests.

How do you accomplish that? Historically "shareholders" as a group have been quite effective (often but obviously not always) have been quite effective at using at their money for society’s benefit.

In fact every society which tried to take all of their money away and eliminate them as a class (more or less violently) has failed economically. Turns out when it works properly free market competition is strongest force for economic and technological progress that has ever existed.

The closest alternative to buybacks is dividends. But to be honest I'm not sure if that's what the critics want the money going.

Stock buybacks and dividends are the same thing economically, I mean both when I say “stock buybacks”. The difference is only in taxation.