lol you could make this argument for any under-thrown back shoulder pass ever. The whole point of a back shoulder throw is that the WR turns his head at the last second so the DB has little time to make a play. But the QB has to have it within the WRs catch radius.
Unless a WR has eyes in the back of his head or a psychic connection with the QB telling him to cut off his route, then that throw isn't getting made. KC did a good job getting the ball out there and not getting sacked, but that ball was not where it needed to be.