This post is intended for 343 but I welcome the opinions of everybody.
I feel like there are a few minor adjustments that 343 could make that is inconsequential to them and makes a tremendous difference for the community. To sum it up: recognition. I have many friends who play Halo Infinite but hardly any of them have seen a campaign all the way through. Back in H3, there was many different incentives to grind it through. Hayabusa for the skulls. EOD for legendary completion. In infinite, the closest thing we have a couple of stances for getting 100%.
What about an armor effect for those who get all 144 achievements?
Something akin to the Katana body piece. Or Achilles for the Spartan companies in Halo 5. Or Haunted in Halo Reach. Or Helioskrill for completing Halo 1-4 on legendary.
343 could add this little incentive and this could bring people back solely for the grind and that reward that a player could potentially brag to their friends about.
Rant over.