In that game, Beasley had a broken leg, Diggs had an oblique injury, John Brown had an ankle injury, and Gabe Davis had a knee injury. Allen's top 4 receivers were all playing hurt and much less effective - as evidenced by the fact that none of his receivers came close to getting any separation the entire game, and had to deal w/ officials allowing KC's DB's to interfere w/ them all day.
We're seeing now how Mahomes is when he doesn't have incredible receivers to throw to. He isn't bored - he's just not on another level from Allen like many fans think.