343 has pretty much been forced to do this because of the enormous drop off in overall online attendance from Halo 4. So many experimental features were more of a detriment than a help (certain AAs, insta-spawns, random weapon drops, etc) overall.
I am thrilled that they're going with a barebones approach to their Arena multiplayer. Natural sprint notwithstanding (and a natural evolution of being a superpowered genetically enhanced war machine) and aside from perhaps Thruster Pack, all the other AAs were game breakers, especially from a competitive standpoint (which if you've known me for a minute in Halo you know how competitively minded I am). If you were just playing to have fun that's another thing but it was still frustrating in many aspects of the game. However, despite all that, you still had to have skill with the weaponry to be successful in any situation. A smart and moderately skilled player could outsmart most other opponents who had otherwise game breaking abilities (although it's just SOOOO satisfying to snipe someone who's crouching in camo).
Anyway, to me this is 343 finally listening to most of the legitimate complaints about how there were too many elements within the sandbox, and more importantly, keeping in mind how important a legit skill based VISIBLE ranking system is to the competitive nature of the game. It's truly amazing how important that is, because in every game with an online MP, you will have the most hardcore gamers vying for the top rank. I see it with FREE mobile games that offer in app purchases, where in order to make the top leaderboard tiers and spots you have to spend money hand over fist (or complete boatloads of offers for the in-game currency) and grind it out. Now of course those games don't require any skill whatsoever in the sense that most console games require you to have to be the top dog, but the biggest downfall of Halo aside from the gameplay taking a dump, was the fact that the ppl at Bungie and 343 alike completely underestimated exactly that point, that ranks were extremely important to more people than they realized.
I really hope this brings a ton of ppl back to Halo, because I think COD is really starting to get stale in many players' eyes, and Titanfall is not doing well (although admittedly this is pure conjecture from friends I have in the gaming world). I can understand ppl still wanting AAs in a non-ranked or non-competitive aspect of the game, and I would support having a separate section for those players, but I also believe that too much separation of playlists and gametypes splinters the community at a time in which it needs to grow back together and regain the strength it had in the past. Maybe if they decide to do a Firefight/Spartan Ops style of game again, they can keep most of those aspects there and stay true to the storyline. But there definitely needs to be a balance between being Master Chief and being the man, and playing competitively with a comprehensive ruleset that evens the playing field for everybody, and allows skill and teamwork to be the focus.
TLDR, this is good. I can't wait.