I love H5 multiplayer, in many ways I think its the best. I agree with some of the balance issues brought up.
My gripe is with the campaign, it is the worst in the series. And that's including Reach, which though it was cool, retconned one of the best books of the best trilogy of all of halo lore! A huge part of what makes halo special for me goes beyond the multiplayer experience. Its the story, the lore, the mystery. Let me preface, I actually don't mind Cortana, or a false variant of Cortana being the antagonist, my gripe is with the execution of the campaign and the awful betrayal of the advertising! That, and the betrayal of about half of what halo 4 set up brilliantly!
Halo 4 recognized that fighting covenant perpetually would be tiresome, so it set up a really cool and complex (if you get into the lore) final boss of the covenant in Jul M'Dama while setting the stage for a much more frightening enemy, the didact, and whatever hell he might unleash via flood and/or Prometheans. Halo 5 ditches Jul M'Dama right off the bat to send a message that Osiris is bad -Yoink-, but all it really says is goodbye cool side plot... Oh and the Didact was apparently killed in cannon but out of game? Look either KILL him in H4 or bring him into H5, they did neither, another huge waste.
Ok so that sets the stage for the cool marketing that Chief now is the bad guy, enemy of the state, may or may not have done questionable things!, mind you this could all be possible in the scope of the plot lines H4 set up, no need to ditch them. So anyway, here we are hoping that Chief is stuck in a complex ethical struggle with morality vs responsibility with whatever the new plot throws at him (H4 was hinting at this) but no. Nope, he is just doin the grind being a good spartan and when he decides to go chase after visions of Cortana (no real stakes for the other characters) he gets chased by Osiris for a couple missions. They get into a fight, by the way could you imagine how cool it would have been to be in a boss fight against the Chief himself?! and one that is unwinnable! fight until he defeats you/restrains you, and goes his merry way. Missed opportunity. So anyway, this doesn't last, it soon becomes clear what is going on with Cortana and they all become buddy buddy again, no stakes.
Again, I don't mind the plot of Cortana or some variant of her as the antagonist. The plot issues here predate that, and this plot could have been rolled in to a much higher stakes ethical struggle for chief making it much more aligned to the marketing.