I mean, admittedly I also play COD. But I only really put time into BO3 as it's the only one I've really enjoyed so far.
But I do understand where he's coming from. COD can be different because you play against different people with different setups/playstyles every match. Overwatch... uh, not so much. And well, Destiny is an "MMO", an essential part of "MMOs" (I put that in quotations bc it's not really) is that they are grindy.
I personally can stand an incredible amount of grinding and repetition for little reward bc when I was little all I played was f2p korean mmos :^)