Five mana is a lot for a tutor, even more so for one restricted to instants and sorceries
The absolute power level of Sphinxs Revelation as in how strong it is as a card in a vacuum is through the roof, but what about contextually in this format at this time
More importantly, Wizards has moved the goal post back on pretty much all dangerous card types, to the point where even if it makes a mistake, the mistake likely won't lead to a ban-worthy card
For this, we have Chainsaw, Mjolnir, Hammer of Thor, and Assimilation Aegis
The inner parts can be taken out and it allows for a modular system of sorting when dealing with large amounts of unsorted cards
Onakke Oathkeeper does a lot for two mana