This has changed in recent years as Wizards of the Coast has been upping the power level of newer sets while also extending the lifetime of cards in Standard, but Standard is still the best format for players wanting swift changes
Sire of Seven Deaths Aside from the creative use of 7 in this card, Sire of Seven Deaths can pack one heck of a punch
Let's consider three other levels of sentiment
For example, even if your opponent brings Solosis into the Active to get an easy KO on it with Sky Return, you can always search for your other Solosis, put in onto Ditto, then Rare Candy to evolve it on the same turn
Maybe youll use Snorlax [Astral Radiance] with Therapeutic Energy [Paldea Evolved] to escape falling Asleep or use Drapion V [Lost Origin] against a Mew VMAX [Fusion Strike] to score a massive OHKO
Tutors are great even outside that combo though because they get what we need at the moment