If Urgot can have a damage penalty to on-hits, why couldn't pre-revert Kog'Maw?
Part of the reason Riot said they partially reverted the Kog'Maw rework if I'm remembering correctly is because his W design made the items it synergized with unbalanceable. Riot's solution to this with Urgot was to drastically reduce his on-hit damage while W was active. Why was it out of the question for Kog'Maw to receive the same treatment?