: I wouldn't really go that far.. I don't know why I would use a light rifle
: over another weapon in campaign other than it does more damage, I don't
: know why I would use a boltshot unless my suppressor is out of ammo, and I
: don't know why I would use the incineration cannon unless I don't have
: other explosive weaponry.

: There is also a communication problem, as we know human weapons are good
: against health, covenant weapons are good against shielding, so what are
: forerunner weapons for....? Breaking promethian armor and killing them?
: Then what would I want to use the other 2 factions weapons for? Despite
: the knights being an improvement in this game, their lack of shielding
: makes the plasma pistol useless against them, as it is against the
: soldiers.

The rationales you described go alongside the human sandbox, though. Halo CE is the only game where Bungie didn't attempt to provide alien analogues to the human sandbox, and that was largely by necessity (since starting with Halo 2 you'd be playing in places where you couldn't presume to have access to human weaponry.) The same rationale holds for Halo 5, although they used the Guardians pretty well as an excuse to bring in Covenant and human materiel.

I think Forerunner weapons distinguish themselves pretty well. The Suppressor has a high rate of fire and strips armor, the boltshot homes make it an effective weapon if you aren't headshot-capable, the Incineration Cannon gives you the choice between more tactical use of ammo or a big honking explosion. That's not far off from the FRG giving you weaker, anti-infantry bouncy projectiles, or the Beam Rifle being more effective for people who go for body shots versus headshots.

The general neutering of the noob combo I think is a pretty brave choice, and one I applaud 343 for. My complaint with previous Halo games at high difficulty, starting with Halo 2 was that plasma pistol + headshot weapon felt like the only way to play; there were times I was loathe to even pick up a power weapon because its use felt outweighed by my lack of utility elsewhere.

Halo 5, meanwhile, mostly makes the main requirement for lethality in Legendary accuracy and effective use of the squad AI. Once you figure out what range your AI is effective at you can use them easily to melt troublesome soldiers or to marshall a bunch of power weapons on a Knight, but the armor stripping feels more like a layered miniboss encounter than the old "overcharge - headshot - rinse - repeat". I love that for the Knights and Wardens you can try for assassinations once you've sufficiently damaged them, or that Knights will scream and reveal their 1HK zone briefly, making your positioning very important for the quick takedowns.