The colorless aspect means every deck can toss it in, like The One Ring
(To mill a card, a player puts the top card of their library into their graveyard.) There is no line Jon Irenicus would not cross to regain his lost immortality
Courage could certainly have done with being a 4/3 or gaining +2/+0 and Haste itself
3 Dragon Dragon types are weak to 3 types, which they receive double the damage from: [4] Dragon - Often considered to be so powerful that they can only be beaten by other dragons
If you want to ramp then the green options typically outclass the Simic ones, if you want to draw cards or counter spells then it is the mono blue cards that are top of the pick list
There are lots of spells that can destroy artifacts and enchantments, but to wipe out a battle you'll generally need 'non-land permanent' removal, or an effect that deals damage 'to any target'