But religion is not gone from Civ 5. In addition to the religious buildings and wonders, there is also the Piety social policies. What you mean is religion has been removed from diplomacy and cultural expansion which I agree, that is a very good thing. There's no reason to give a diplomatic bonus to nations of the same broad religion, because they historically have a rich history of slaughtering one another due to the numerous sects and denominations that are found within the broad religions. Protestants vs Catholics for example, Shia and Sunni another one.