You have to ask yourself, particularly as a shareholder but also a member of society, do you want the company to extend into other industries where they could not only be over-extending themselves beyond their core competency but also over-exposing themselves to macro-economics, geo-politics and anti-trust issues.
Do we want all companies to chase monopolies in multiple domains like Amazon? Should Verizon/Comcast/etc. use its monopoly profits from telecom to go after media, then cloud computing and then conquer consumer goods and healthcare or should it just return profits to share holders? If the money goes back to the shareholder, then the shareholder can go find the category leader in those other domains and invest it more wisely.
That said buybacks can definitely be manipulated by some management teams to game their compensation, which is a definitely bad thing.