If you get to untap with Vivi Ornitier https://scryfall.com/card/fin/248/vivi-ornitier , you win the game. That's an oversimplification, but not much of one. It's just too much cheap mana too quickly.

Standard (atm) is too fast and too tight. Miss a land drop you're dead and it's all (effectively) over by turn 4 in even the (rare) non-aggro non-combo mirrors.

Izzet Prowess decks were 42.3% of the entries for Standard Constructed the FF Pro Tour and the vast majority were running 4 copies of Vivi Ornitier in their main.

Stop this mega-aggro mega-ramp madness.