It shall remain in its Vintage containment zone forevermore
It can effectively shut down graveyard strategies in any format, from the Dredge deck of Modern to reanimator commanders such as Sedris, the Traitor King or Meren of Clan Nel Toth (and it can be cast for free in the opening hand)
Tomb of Annihilation doesnt need to go in your deck, and venture into the dungeon effects are plentiful, meaning you can conjure The Atropal almost as an afterthought
Each one ensures you can start playing right out of the box
While this was partly because people simply assumed Dredge couldn't work without the banned cards (without Dread Return, the Bridge from Below combo doesn't work, and without the combo, traditional Dredge was off the table in Modern), it's also that the deck was simply lurking behind the scenes, waiting for the right pieces to be printed