With how often people complain about how 343 handles Halo, I never hear my own biggest issue:
343 pushes the fantasy elements HARD and forgets to approach it as a war story at all.
The original Halo games' narratives were war movies in a sci-fi fantasy setting, not sci-fi in a military setting. That is, it was a war story first with fantasy set dressing. The earlier books and Halo: Reach took this approach the strongest, but that was the priority for Halo's story for Bungie's entire run.
Basically all of the grounded but glorified approach to war that you'd expect from an American propaganda film, but set in a sci-fi universe with sci-fi bad guys.(another example of this style of story is the movie Battle: Los Angeles)
Even in the more fantasy leaning parts of the original trilogy, the UNSC and the Covenant had the appearance and feel of a functioning military, especially in terms of how characters interacted with each other outside of combat.
The sci-fi elements on the humans' side were also much more grounded than 343's interpretation. Outside of spaceships, the games, books, and other media always mostly showed humans using technology that, to some degree, already existed in the real world at the time, only inserting sci-fi on the humans' side where it was necessary for gameplay or to facilitate events in the story.
343's portrayal of how military personnel (Spartans moreso than normal soldiers) interact may as well be ripped from an MCU film, and most of their sci-fi leans WAY harder into fantasy than Bungie ever would have.
Beyond the contents of the narrative itself, I grew up in a city with a population that was 2/3 active military and veterans, and I went to a public high school that was on an active military base. Tons of people everywhere from ROTC to the actual military preferred Halo over other games because its story portrayed military personnel more accurately and respectfully than more "realistic" shooters like Battlefield and CoD. I've heard from other people that this sentiment didn't end at my hometown.
Halo Infinite managed to correct or compensate for a lot of the problems with earlier 343 titles, and Halo Wars 2 brought back the best of the old visual elements, but I'm worried that what made Bungie's Halo stories stand out might be gone for good.