In short yes, halo 6 needs sprint. halo 5 is my favourite gameplay style out of all the games, yes halo 3 was great and is my nostalgia game, I look back and go that is best experience but in all honesty its not, and I know that by playing the MCC, nostalgia clouds a lot of peoples judgments. I think halo 5 has the best gameplay and has for want of words perfected it so far, the thrust packs, sprint and wall clamber (forgot what its called unless it is that lol) is all what is needed, not the ability's of reach.
The gameplay is much more fast pace and action based with sprint, when I did play on say like halo 2 or 3 on the MCC it feels so slow in comparison, sprint is a basic ability and how 343 have handled it is great with the fact that your shields do not recharge while sprinting. It adds another element to the gameplay and enhances it.
As for the people that say sprint lessens the skill gap, no it doesn't, the skill gap is still their, but to be a skilled player you now need to be skilled in sprint as well, and I know its not like this for everyone, but just because a player was highly skilled at halo 2 and not at halo 5 does not mean the skill gap has lessened, just that they are no longer as skilled/ or at the same level of skill for this game as they were for previous games but they still think that being skilled at halo 2 means they are skilled at halo 5 but because they are dying more because of the use of sprint the skill gap has lessened, that is not the case, they are not at the same skill level any more