Based on what metric? What does that even mean?
Honestly, I think this mindset is part of why Reach failed competitively. Stripping everything out to make the game line-up with some romanticized, god-tier vision of a Halo gone by just makes the game unappealing to people - "casual" or not. Embrace the new mechanics, or lose. If they REALLY can't function competitively, then sure, take them out, but come on, at least keep an open mind.
Reach failed competitively because out of the box the game was bad competitively. Bad maps, Bloom, Sprint, AAs on spawn, slow movement speed, limited agility, etc. all made the game not fun to play at a competitive level for a lot of people. Competitive gametypes aren't just created with the mindset of getting a lot of people to play them. It certainly influences some decisions but in the end the gametypes have to be fun for the competitive community. I think most people in the competitive community would love it if MLG didn't strip away half the game but if the default settings are too casual than something has to be done.
The AR and SMG are both one-dimensional and have a relatively small skill-gap, they were removed. Radar was too much of a crutch for bad players, without it people would have to rely much more on situational awareness, it was removed. In Halo 3 equipment slowed down the game and were essentially invisible back-pocket safety-nets, they were removed. Bloom + sprint in Reach slowed down the game tremendously and often made the game frustrating to play, both mechanics were removed.
Mechanics and gameplay additions aren't just removed or altered to make the play more like Halo 1 or Halo 2 like some people seem to think. They're changed simply because it makes the game play better competitively. You can include everything in a hardcore or MLG playlist for the sake of making it more popular but if it's not competitive then there's no point in having the playlist in the first place. Most people don't know this but MLG always starts off with settings that are close to the vanilla Halo game. I'm pretty sure even Armor Lock was in one of the earlier Halo Reach MLG gametypes. It simply didn't work, so they removed it.