In my opinion, yes, techs could take over the job of a pharmacist and probably still perform well enough to satisfy the overlords. But, for those mistakes which can and do happen, they will be missed, and there will be harm done. Techs do not have the deep level understanding of drugs that pharmacists do in order to make the right calls on drug interactions or therapy changes, and I would imagine that such an understanding would be very difficult to self-teach. Techs can learn basic info on drugs from working in a pharmacy, sure - but there's a lot of thought process by good pharmacists that aren't vocalized.
Pharmacy school is also quite rigorous and requires someone who is either quite intelligent or quite disciplined to pass (well, I guess it used to). But many technicians are neither, so that is (was) yet another filter that a person with a pharmacist role has to pass.