The formats been harsh to control decks, but never enough to leave Teferi totally out
I didn't know a thing about efficient deck-building, tournaments and the like, so it couldn't have been that
However, cards with Vigilance may attack during your turn without being turned, so they arent considered tapped
The card's pretty darn strong too, protecting your whole board of characters by reducing everyone's strength for one whole turn cycle
Dihada will be happy with this for sure
However, one mana is a very low cost to have access to a wide toolbox of creatures of any color, with no cost restrictions, and any archetype with creature-based combos and/or that wants to take advantage of more of the famous hatebears can take advantage of this spell in some way