While I never found religion to function as any more than a support system for your Cultural policies and other interests in Civilization V, I have to say that it's immensely preferable to what we have now with Civ VI. First and foremost, the whole system seems to be broken. The AI can spawn seemingly impossible numbers of apostles to send at your territory, making it very difficult to combat them all and keep your own cities following your native religion, let alone trying to proselytize beyond your own realm. Sure you can ask other Leaders to stop sending them, but frankly that hasn't ever worked so far for me; the AI behaves in the same exact, fork-tongued way even if they say they'll comply with your wishes. So what about killing the enemy religious units? This mechanic is seriously funky on two fronts. First, there's the silly lightning bolt animations when you engage in theological combat. Who thought this was a good idea in a game that's supposed to be at least fairly grounded in reality like Civilization? And then we come to the elephant in the room, the biggest reason you can't simply shut down enemy religious incursions: unlike in Civ V you can't attack enemy religious units with anything other than your own Missionaries or Apostles. This renders your armies useless to act as deterrents. Personally I very much preferred Civ V's system where you could warn another Leader not to continue proselytizing your citizens, and then if they didn't comply you could decide whether to risk war by killing them off. That makes so much more sense than having magical battles and trespassing enemy units that your military pretends don't exist.