I am not a fan of UE. It usually only serves to introduce the same problems to all games and similar feel.
But aside from that... I don't care what engine halo uses. 343 never made a great halo game and infinite was absolutely terrible.
I even liked the new cortana and the beard pilot guy. He was great. Cutscenes were great.... but the flow sucked, open levels sucked, every boss was a monke and 2nd half of the game was a corridor... again