I used to watch MLG events for H2 and H3 and loved them. I thought H5's gameplay was boring by comparison. The maps just seem monstrously oversized, there were seriously long range BR duels happening in the midship remake's bases, which were traditionally cqc-mid range oriented.
I just don't find large maps to be exciting and ESport worthy at all, it's just too easy to aim at the opponent when you're that far away from them. In the original trilogy if you got in a 1 on 1 fight in a specific room on the smaller maps you could jump, strafe, Gandhi hop, and crouch to throw off the opponents aim and force them to move their reticule to an extreme to keep up with the rapid movement. In Halo 5 it looks like most fights will be at such a large distance that all of these techniques will be nearly pointless, because no matter how much someone moves they're going to constantly be in your FOV, which means that it will require very little effort to keep them in your cross hairs (even with the decrease in aim assist).
In short, the game just doesn't look as if it will be exciting enough to watch to become an esport. The only way I can see it taking off is if Microsoft puts a lot of money behind it to get people interested in competing.