As the other comment said, the MCC was a remaster. Most of the changes were cosmetic, to the point where it actually had a button to switch between original and remaster graphics, since it was the original engine running everything. The level design, mechanics, weapons, and such were all untouched.
The new Halo remake is a completely different game made in Unreal 5. Already from what has been shown it is very divergent from the original in many ways. This announcement is an intention to do that for the other games.
As the other comment said, the MCC was a remaster. Most of the changes were cosmetic, to the point where it actually had a button to switch between original and remaster graphics, since it was the original engine running everything. The level design, mechanics, weapons, and such were all untouched.
The new Halo remake is a completely different game made in Unreal 5. Already from what has been shown it is very divergent from the original in many ways. This announcement is an intention to do that for the other games.