The Mooncancers include BB and Kiara, both of whom are world ending entities. And also Arc, who is arguably more powerful than Oberon is.
The quality doesn't matter here, only the quantity.
And in Quantity, there is very few Pretenders and MoonCancers in comparison to Alter-Egos, Rulers, Avengers and Foreigners we have had that ultimately made us "alien" to the Human Order.