It has good stats for its cost, provides minor, repeatable graveayrd hate, and even gives you cost reduction with the right set-up
Moxen are generally dangerous in fair formats, so we're cautious about where we allow them to be played
Having too few tutor targets can make your tutors useless, while having too many can dilute the effectiveness of your deck
So, the bottom line for the mythics is this: the value is good, probably better than most people expect, putting the set on par with Modern Masters 2017 in terms of average mythic value, but the variance is going to be problematic for people only opening a small amount of the set
Grab Dragonlord Dromoka
It won't consider any cards in your sideboard, so those cards don't have to follow the deck-building rule