Because she has haste, she can immediately impact the game on the turn she arrives
Flashing back an Opt with Snapcaster Mage may not seem like the exciting play, but its an important one to have in the bag, especially in matchups where you need to get aggressive like combo or Tron
Unfortunately Starfield looks for the card's mana value and with both doors unlocked, the mana value of the enchantment is 0 and so it'd die and go to the graveyard because it has 0 toughness
Maybe more if youre sucking counters off things like Liberator, Urza's Battlethopter
Functionally, what this effect says is that if you can attack with The Lord Master of Hell, and you have 40 or more cards in your graveyard that are neither creatures nor lands, you win the game
Theres actually a lot of strategic decision making that comes from wheeling cards, though thats less true in the age of Play boosters