Battlefield Scavenger

Oracle Text
You may exert Battlefield Scavenger as it attacks. (It won't untap during your next untap step.)
Whenever you exert a creature, you may discard a card. If you do, draw a card.
Card Rulings
4/18/2017 You can’t exert a creature unless an effect allows you to do so. Similar effects that “tap and freeze” a creature (such as that of Decision Paralysis) don’t exert that creature.
4/18/2017 If an exerted creature is already untapped during your next untap step (most likely because it had vigilance or an effect untapped it), exert’s effect preventing it from untapping expires without having done anything.
4/18/2017 If you gain control of another player’s creature until end of turn and exert it, it will untap during that player’s untap step.
4/18/2017 Some cards have abilities that trigger whenever you exert any creature. These abilities trigger when you exert that creature or any other creature you control.
4/18/2017 All cards in the Amonkhet set that let you exert a creature let you do so as you declare it as an attacking creature, as do some of the cards in the Hour of Devastation set. You can’t do so later in combat, and creatures put onto the battlefield attacking can’t be exerted. Any abilities that trigger on exerting an attacking creature will resolve before blockers are declared.
Those are just the cards with 2 power and upsides. Blue creatures are generally more defensive in nature, so it gets things like Thing in the Ice, Shielded Aether Thief, and Doorkeeper to hold down the board when the opponent is playing things like 2/2's on the same curve so you can keep board presence for a few turns while you accumulate value and stall for late-game finishers. That's how blue rolls.
Colors are different. Get over it. Yes, this card is pushed, but did you see Curator of Mysteries?