Taking the Hub and all of the awesome tech and easy answers away from Jack, Gwen and Ianto let us see that without them they were still brilliant, still courageous, resourceful, and tightly bound together. It was what Jim Butcher did to Harry Dresden in Changes, and what Supernatural tried (but failed) to successfully do in Season 7. It’s always risky, and in Torchwood I think it was a good move.
Although I’ll always miss the Hub and I’m convinced Jack, wherever he is, has small ones all over the world now. Torchwood’s more mobile, and more global.