Let's just clear a few things up here, people.
1. I highly doubt Chief's face will ever be shown. Keep in mind Frankie is head of development. Someone who played a key role in the creation of the first 3 games. He knows what makes Halo, Halo. With that in mind, it is also their game. We were aloud to see the chief's eyes because of a reason. 343 put that in to kick off their trilogy. The idea behind it is the same as when Chief removes his helmet in CE. And yes, I am aware you do not see any of his face so, please do not respond with that reply.
2. Cortana: There are 2 more games left in this trilogy. Frankie specifically said that this TRILOGY (not just this game) would focus on the relationship of Chief and Cortana. Did you ever stop to think that losing her and having to fight to have her again (after their relationship is that intensified from 4) would be incredibly touching. How into that would most Halo players be? The relationship for Chief and Cortana was taken to an entire new level in Halo 4. Sure, we've had to fight to go get her twice in the first trilogy and it was pretty intense. How do you think it'll be this time? I'm pretty sure it'll be a tad bit more emotional.
3. Forerunners: The game has not left it's original concept of story. Halo CE, 2, and 3 all had Forerunner stories happening while you fought. This is only bringing us the main plot that was originally intended to be.
Simply put, if you don't like it anymore; don't play it. The rest of us who understand that games grow just as we do as people. Why can't the characters change with us? I say it makes it that much better.