I honestly don't understand what people expect. Sanchez is arguably better than our entire forward line, Vucinic included (and I say this, because Vucinic is awesome on his day, but lately he has been 80% in absentia).
Is he a top player? Probably not. Is he a very good player? Most definitely. Is he good enough for this Juventus, and will he upgrade our attack? A resounding yes.
Lloretne and Sanchez will give our forward line a massive boost. Perhaps in 3-5 years when we can afford the Agueros, Suarezes, and Falcaos of this world, things might change/be different, but for now Sanchez is as good as it gets.