I don't understand the uproar about all this. Would these same people be freaking out if they remade GoldenEye but added dual analogue stick support? Mechanics typically change for the better and adding sprint and ADS in my opinion makes for a better more modern experience. I watched the IGN video of them playing a round on the new Coagulation map (Blood lines I think it was called now) and the entire time I was like "Oh my god why is walking everywhere?" forgetting that there was no sprint way back when. I respect the nostalgic side of the game and I am glad they have kept the old school Halos the way they were but I think adding modern mechanics and finding a good balance between new and old would put Halo 5 in a much better place.
As a consequence of sprint, base player speed is slowed down and maps are made larger.
So yes, in Halo 2 you would be walking everywhere. But walking would still be faster than walking in Halo 4, and maps would be smaller than Halo 4 (the only game to officially have sprint).