I am very late to this topic so I probably am not bringing up anything that hasn't been said before but I wanted to weigh in too.
First, every time someone questions whether or not Halo is still relevant, my mind flashes to threads like this one where there are pages on pages of peoples thoughts, opinions, arguments... i.e., their passion for this franchise.
Halo has done so much so well in it's time and ultimately all the griping is really just the sour side of the way that people really pull for this franchise.
The level of salt over this brief article is understandable, from all perspectives, really but it is a lot of fighting over scraps.
We would love for 343 come out an comprehensively account for the more egregious flaws of H5's campaign and confidently detail how they will be rectified. But that is not going to happen is it? The gave is still in dev, 343/MS always plays Halo close to the vest until 6 months or less before release. Leaks are always fun, but are fairly useless except for speculation until confirmed by the final product.
That being said it is unsettling that 343's takeaway is simply more Chief versus assessing a breadth of truly elementary storytelling problems. A well told story is, in part, a sales job for the new characters and elements and 343 simply did not sell them well at all.
Also, something about the gameplay is off, particularly with the squad elements. I, like many, always play through a new Halo on Heroic first and then do a Legendary run. For me, Heroic always best represented the video game challenge of going to war but being the superhero too. Legendary, on the other hand... Legendary, is where you really fought the Covenant, where the desperate story of humanity on it's heels and you as the last hope best sells the scope of the story, the unlikeliness of your victory.
Halo 5 is the first Halo game that I could care less about finishing on Legendary. Every engagement on Legendary in any of the games is all about solving a puzzle as it evolves as much as it is about being skillful. Playing Legendary often means getting cut down seemingly out of nowhere. Repeatedly. But something with the squad made it so much more difficult and cheap. Not to mention, I wish you could skip waiting to be revived. It almost never works out and just wastes time waiting for the next opportunity to get back to the Legendary grind. The squad in H5 just feels like a bunch of goobers constantly getting taken down and whining for assistance.
See I have my own salt too!