You can exile a target Creature, or give the choice over to your opponent to sacrifice an Enchantment they control
Banning is still a tool in our tool box that we will deploy if necessary in the future, and one we would typically prefer over a drastic errata like this
One mana tricks tend to be pretty nice in aggressive decks, as you get some serious tempo when you use them to win combat, and this one definitely gives you enough of a boost to be worth running in those decks
How do we classify Mystic Sanctuary and its effect on the Modern format
Conclusion In recent years, players have focused on the overall gameplay experience rather than building highly optimized and competitive decks
In the case of Ugins Conjurant, youre looking at a free dies trigger, a free cast trigger, and maybe an extremely unlikely place for a tribal Spirits build to dump a whole bunch of mana