Against Flood you're not only dodging bullets, you have to dodge leaping tentacle sweeps, exploding garlic and bombastic fat blobs. You can be reductive against every enemy in Halo if you want ----- Just Plasma Pistol + rifle = ZZZZZZZZZZZZ boring mindless combat what a snoozefest Halo is lameee.
Sniper Flood in Halo 3 were wack though.
So basically what I'm saying is Halo plays best when all enemy types are used well in engaging combat scenarios, which includes how maps are designed for the player to flow through, the AI of said enemies, how the enemies interact with each other + their surroundings, the weapons available to use, etc. What I want for Infinite is to bring back most enemy types so there's enough diversity to fill out the campaign without one piece of combat feeling stagnant, which I think would be a huge deal for fans.
Jet Pack Brutes? Gravity Hammer Brutes? Standard Brutes? Standard Elites? Sword Elites? Plasma Pistol Grunts? Fuel Rod Grunts? Hunters? Shield Jackals? Sniper Jackals? Flood forms including big boiz, popcorn garlic, juggernauts and soldier-types that use weapons and melee attacks? Promethean Knights? Upgraded Promethean soldiers? Shit even Crawlers (which I found interesting in their own right because it felt good to shoot them in the face, seeing all their bits explode)? I'LL TAKE THEM ALL! There's plenty I haven't even touched upon, including vehicular combat.
What I don't want is for Infinite to just be another Halo game with just your typical Covenant enemies in situations we've experienced before. I want to fight a Brute again. I want to fight Flood again. I want to see Brutes fight Elites fight Flood fight Prometheans fight Marines fight fight fight. Give. It. To. Me. 343.