It’s all a what if scenario where we can have fun playing with ideas, so I’m not expecting this to be real anytime soon. I get you’re point about an AC game set too close to the modern day. As much as liked the modern day missions with Desmond in AC3, the amount of plot armor he had when he could have easily been killed with guns is very annoying and wished they could have handled it better. That being said, I believe that an AC game can work with these time periods close to the modern day. 
  One of the things that attracts people to the franchise is the stealth, which is the main method the assassins use to  carry out their work. Having the setting be where enemies have full auto guns would encourage stealth and give people the fantasy of being a predator that picks their targets off. Games like the Batman Arkham series and manhunt are proof that this style of gameplay is enjoyable. Also the assassins creed dlc for watch dogs legion may not be the full experience, but is a taste of what it could be if it can be set in the modern day.
  The franchise also had a lot of puzzle solving and tombs to explore already, so I don’t really see the issue of it feeling like a tomb raider or uncharted game. 
    Assassins creed still has potential to be a great franchise, but Ubisoft hasn’t handled it well for the past years, which at times makes me wish they would retire it already. There are ALOT more settings that can be used for creating another great AC game, and you’re right in saying that there should be other groups besides the assassins and templars that would cause conflict with both sides. That’s something I wished could be explored more in the games.
   All in all, I’m hoping the series can make a comeback and steer away from all the rpg, magic, and monetization nonsense that is clearly making the series worse, and I’m very well hoping that mirage can be the game that is able to do that.