Good morning

Poor organization

But that doesn't seem to matter when they fight *for* the Covenant. The Grunts are literally cannon fodder. In The Fall of Reach (one of the books), their strategy is described as throwing themselves at the enemy until their corpses pile high... and the enemies have depleted their ammunition.

Furthermore, Spec Ops Grunts and Grunt Ultras are given energy shields, which should give them a slight advantage. They're also large enough to operate Shade Turrets, Ghosts, and other vehicles. And, if they're strong enough to be able to carry a Fuel Rod Cannon, they can probably use bigger weapons like Plasma Rifles, Plasma Repeaters, Needle Rifles, and even Covenant Carbines.

I don't think they organized any of that though. Sure, they have access to those weapons, but without good leadership, anything they do sort of falls apart. Without elites or even jackals to keep them in place, the grunts would have likely left the covenant a long time ago.