I think I mostly agree with you (give or take the English speaking Covenant bits, because it can work without English [H1 Elites], but the Grunts seriously could use that English [Bungie/343 issue here]), and you did a great job of conveying that they really suck at writing. I mean, you really hit the nail on the end. The part where they should be "showing" and not "telling" never seemed to work from them, both from an in-game story perspective and from 343 employees doing a lot of telling and providing incorrect assurances about the writing and story.

The next problem is that 343 stuck with their guns so much that if there's this huge radical change in emotion and direction in H5, it will make the overall whole of the story break the suspension of disbelief. Like if all of a sudden out of nowhere these Prometheans start acting completely different with almost no explanation, it would be out of their (lackof) character that was established in H4. They would need a story based reason for some sort of change or hesitation in why all of a sudden these things might start showing signs of humanity. It's very do-able. The question is, can 343 do it?

Another example would be if all of a sudden they make Palmer some nice and caring individual who suddenly respects scientists and isn't just a terribly written piece of garbage character that needs to die. That radical of a change with no explanation beyond "the fans hate this character no matter how much we're trying to pretend that they don't" would just be ridiculous and forced. They went down this path kicking and screaming, and they're stuck in many ways unless they start getting some major narrative work going to fix these glaring character (lack thereof) problems with the writing.

Or they can just focus on putting Spartans into random sand ponchos because "looks cool" and "why not" and "fly it into the sun because who knows what else to do at this point" and such.