Because Halo perfected it's fair dance long ago and whilst every entry within the MCC's unique in places, the only mediocre one's still the best COD, and 343 Industries' first attempt's partially saved by a highly emotional narrative. Whilst no other entry's like Reach or ODST in a good way.
Guardians' also significantly unique from every other one before it in a bad way. It's attempts at evolving did not succeed ironically because at it's core Halo means identical starts for everyone and learning to use the three pillars of guns, grenades and melee to best opponents, whoever's most skillful at using the tools at their disposal wins something unfortunately no longer the case for the majority of this genre anymore, so I ultimately must agree to disagree as it may be outdated on a superficial level, but with barely any recent exceptions I only hold contempt for the majority of it's overly flashy contemporaries.