5 mana for a threaten just feels like too much, even if the creature does get menace
Niv-Mizzet, Parun Good ol' Niv-Mizzet, Parun is here to kill foes, draw cards, and chew jalapeo-flavored bubblegum
When they counter your artifact spell, it goes to the graveyard, and Mishra simply puts it into play, completely ignoring the downside while your opponents are stuck paying taxes
There was a deck that floated around Standard on MTG Arena that tried to use the surveil suite that was so good in Guilds of Ravnica Limited with a few other pieces
Illuna, Apex of Wishes is tougher, more powerful, can fly, and has trample
Boros tends to do better within the Standard format because it's one-on-one and 20 life points