You can just use it at the end of your foe's turn and then untap and go on
When Sparkling Crystal is attached to a Tera Pokmon, which Dragapult ex is, that Pokmon's attacks cost one less energy , allowing for Dragapult players to use a strong move like Phantom Drive much sooner, or even use Jet Headbutt without needing any energy at all
Granted, U/W/R has ways to beat any and all of these cards, but its difficult for the opponent to have them all at any one time
These effects are so much better when they give you a way to clear lands off your library, and this case gives you up to two land drops off the top each turn
Being able to get rid of Indestructible creatures is a relevant bonus
As an uncommon that was reprinted in Time Spiral Remastered, Delay isnt worth too much