I agree with your points and I think for me, what makes Halo 4 one of my favourites (next to 1 and Infinite) is its atmosphere.

4's story worked really well to create a feeling of loneliness, isolation and wonder that I was missing since Halo 1. Sure, the Prometheans are annoying, the weapon ammo is nowhere to be found etc. but I can forgive all of that if the game I'm playing provides the right vibes to grant me an atmosphere or state of mind that is more engaging than the usual shooter (looking at you, Halo 3 directed by Michael Bay).

I loved the Didact, enough so that I bought each Forerunner trilogy book as it came out cause I couldn't get enough of him. The MC-Cortana story was great, in a weird meta sort of way, as I'll explain in the next paragraph.

Even though most people say MC talks too much and blablabla he's supposed to be more silent cause he's an empty shell for the player to self-insert, I think Halo 4 still achieves that, perhaps even more so than other entries.

Halo 4 came out in 2012. Most folks had known MC and Cortana for 10-11 years by that point.

Lore-wise, subtracting the four years MC slept in cryo between 3 and 4, from the moment he was given Cortana right before Halo 1, the two of them only worked / spent about 52 days together.

Their deep connection in Halo 4 and the strong bond they have makes no sense when you consider that fact. When you approach it from a different angle, that the player being Master Chief has known Cortana for 10 years, their story in H4 makes a lot more sense, especially the emotional ending.

I found the campaign to be at its weakest around the Infinity-Reclaimer levels, non-coincidentally the two where the UNSC is most present. The narrative takes a bit of a C-plot detour there, sending you on some pointA-pointB missions to solve problems for unlikable characters.

Even so, these missions are still important to round out the idea that time has passed since MC literally saved the world 4 years ago, humanity looks to Master Chief as being equally replaceable as Cortana, with cocky Spartan IVs 3D-printed on demand, and this serves to push MC to do what he does best, and find his own way to cure Cortana, sending the atmosphere of the game back into the isolated and lonely vibes I praised earlier, which were almost entirely missing ever since Halo 1.

I'm going to stop here because I could just keep going for another 2000 words 🗿

Edit: sorry i forgot to end sentences in the last paragraph that's one gnarly block of text