Zariel does just one worse with +1/+0 and haste for her +1 ability for one less Green mana and four mana total
That said, its almost like a staple in cards that care about going wide, tokens, and the like
three mana to draw five is fantastic, especially in coordination with cards that want you to fill your graveyard
If youre waiting for a window where you can resolve a six mana creature and a five mana enchantment, thats less of a window and more of an entrance to an Apple store
Build a deck around instants and sorceries, and Delver of Secrets basically becomes a 3/2 flyer the turn after it comes into play
To determine the total cost of a spell, start with the mana cost or alternative cost you're paying (such as an overload cost), add any cost increases, then apply any cost reductions