Hard disagree. Every single weapon in Halo 3 comes down to the skill of the wielder in conjunction with their functionality. Someone with an AR who knows how to use the map and the other weapons in their toolbox to their advantage can rack up kills. This is not the case with Infinite. Infinite’s AR strongly encourages close-range fat fingering the fire button, and to pulse it at longer ranges.
Thank goodness that Halo 3 has a plethora of options to supplement the utility of your AR, such as Equipment and three types of grenades you can carry simultaneously. People seem to forget that the weapon in your hands is not the only thing you have for killing your opponent. Your Equipment, Grenades and Melee, and effective utilization of the map can give you the advantage in situations where you otherwise would not.
Slightly unpopular opinion, but the BR isn’t the be all, end all for the Halo 3 sandbox. It’s obviously very good, but has competition in the form of the less often seen Carbine, is outclassed by the frequently spawning Sniper Rifle, does not perform in close-range well against the Shotgun, and can be outdamaged by a number of paired weapons in close-range. A Battle Rifle does not confer an immediate victory over everyone who does not have one, skill plays a larger factor in whether you get a kill or not when it comes to Halo 3.
My problem with every Halo game past Halo 3, is that there has always been a weapon that stands heads and shoulders above all the rest, to the point that you keep it with you all of the time, and what makes it worse, is that they’re a starting weapon. The DMR in Reach is by far and away the most useful weapon that you keep with you all the time. Same story with Halo 4 (though it was often supplemented by the aggressively OP Boltshot). Halo 5 had the Pistol. Halo Infinite has the Assault Rifle. These weapons are so useful beyond an intended role for them, that you devote a slot to keeping just them around.
My beef with the Infinite AR is that it makes so much of the sandbox less useful, and I think removing it or nerfing it would result in people using a more varied spread of weapons than just the AR because it’s such a powerful Jack of All Trades. The AR in Infinite compounds the vast issues with the Infinite sandbox, where so many weapons just are not that good unless they are power weapons.
Halo 1-3 were designed as pick-up shooters where you regularly swap weapons so that you use a plethora of different options based on the situation you were in. Halo CE kind of fumbled this, Halo 2 had it a little better by having players spawn with SMGs often, and Halo 3 fulfilled this by having weapons that were harder to use as starting weapons, to encourage players to find more weapons in the environment and utilize them as opposed to sticking to weapons they spawn with that slot them into an incredibly stale meta.