As much as I try not to say anyone's interpreting a story wrong, I think this guy got it wrong. Bungie wanted us to think Halo is about being a hero, and 343i still does want us to think that, or maybe they really do think it's about heroism. They've said as much directly and people in-universe keep calling the Chief a hero.
The problem is the story really isn't about that.

There are only a handful of instances in the whole series where you do things that aren't strictly necessary, either to live or because of your orders. I would not say a soldier killing things he has to kill, pushing buttons he has to push, breaking things he has to break, delivering things he has to deliver, is being a hero-- brave maybe, strong, determined, but not a hero.

Heroes go above and beyond.

The vast majority of reasonable people who have the ability would do what's required of them to keep their job and defend their life. Even for most of the larger-than-life situations you get put in in Halo, it's usually not heroic because, well, if you had the ability to the save the world, and it needed saving, what would you do? Do you think you're a hero?

Does the fact a character actually acts and follows through make it heroic? Does risking your life to save the group/species/town/planet/galaxy really mean that much if you risk your life every day anyway? What if you chose that job, that life of risk, and you've been trained to think of it as acceptable and even good, or you chose it because you already believed that? What if you didn't have a choice and had it ingrained in you from a young age?

What about the meta-view, is it heroic if you need to do it to finish the game, so you're going to regardless of moral implications? If you don't have to, is it heroism that you can attribute to the character if it was actually the player's choice, and the character never acknowledges it?

No, the Chief and the other protagonists mostly (not entirely, but mostly) do just what comes naturally to human beings in general and soldiers in particular-- and that's good, it's commendable even, but it doesn't make them heroes.

Since heroism rarely happens in the games and it's never an element in the larger plot* it can't be what the stories are about.

He's doubly wrong because 343i made Halo 5 more about heroism of a sort, or at least paid it lip service-- during a bunch of Fireteam Osiris missions Locke has voiceover about helping people even though they have no orders to that effect. I will say though, those are almost all either so that Governor Sloan will let you progress, or are referring to the Swords of Sangeilios, who largely don't need your help and who you need help from to progress in several spots, so their attempted heroic elements do fall kind of flat.

He also seems to have not grasped some story elements despite playing all the games and caring about the story and getting into the extended fiction, or if did he didn't get that across. The Didact is explained and expositioned not just by the books but by terminals in Halo 3 and 4-- and that should be just as good a reason to not like him, because they don't agree with each other or the version in the cutscenes. Halsey has reasons to be treated like a bad person, the issue is with the shift of how much each character does it and why (and if there even is a reason), and that Halsey seems incapable of defending herself without after-the-fact reasoning (and if anybody should be able to make their case, it's Halsey).

I'm also nonplussed about his assessment of the gameplay, a lot of it seems on the money but some parts just don't make sense. I can't figure out how he had such a hard time killing a simple Promethean Soldier on Heroic, and I wonder how low on health he was when he decided to punch it, and how occupied the fireteam was when he told them to target that Elite. I would argue the Warden Eternal isn't a boss fight precisely because it shows up again and again and sometimes with several at once, and I didn't think it was that bad (it didn't start getting frustrating for me until the middle of the very last fight on Heroic), but there's no arguing with the fact a lot of people got sick of it or that it's uncreative.

* except for Reach, and even then there are caveats: the end of Long Night of Solace has Jorge being heroic (possibly beyond reason), and it's very much a plot point, but it's not the player character or anyone the player character demonstrably cares about; Exodus and New Alexandria could count, although Noble Six and the rest of the main cast say nothing about them, you have to kill most of the enemies to progress, and they don't connect with the larger story of the game; Emile has his moment in the last level, as does Noble Six, but Halsey (who has the backing of ONI) assures them this package must make it off-world if humanity is to have a fighting chance so it's the "saving the species" problem again