>>96761323
The Guard is cost-efficient, but not particularly 'good'. They emphasize quantity over quality. And for a while this did work against a lot of enemies.

The problem is that none of the factions that are still around have the 'drown them in bodies' strategy work against them all that well. The Eldar have a lot of mobility and can move their entire Craftworld to another location, the Orks literally create more Orks by dying, the Tyranids will just eat the corpses you're throwing at them as well as their own corpses to make more Tyranids, the Necrons just regenerate and come back with endless waves of robots, the Tau have heavy firepower and a lot of mobility so they just shoot and scoot whenever the human waves get too close or they target your logistics instead, Chaos has functionally infinite amount of daemons to throw at you, etc.