There are so many low cost enchantment cards in standard right now that get played very early on and, if you dont have a response they can ramp out of control in a matter of a few turns
Regardless, the more interesting part of Mondrak is his role as a sacrifice outlet
Their are cheap dorks which survive this so it doesn't have quite the same early game control as Smother but it is a sufficiently well rounded and better card overall that it is the more desirable cube card
If an effect allows you to search your library for a card with mana value 4 or less, you can't find Bottomless Pool // Locker Room
The end result is a deck that is low to the ground and casts lots of spells per turn, swinging in each turn to chip down life totals and then closing out the game with a combination of burn and creature combat
I know power creep is a problem in Magic, but you dont expect a legendary mythic to be superseded by a nonlegendary rare just a few months after release