Kinda nuts they didn't show off more, and what they showed didn't really showcase how things have evolved from last years demo
That said, the Cortana story elements have me excited -- if they bring forward the emotional core and story threads between MC and her that Halo 4 really leaned into, I think the story will be in a great spot. Also, I can't imagine this is a whole refresh from Halo 5 -- I imagine those story elements are in play, but over the period of the game we discover how, etc.
That said, I wasn't a fan of Halo 5's direction or ending, so I do appreciate a redirect to a degree.