I can't Mikael's Crucible Galio's ult

I was playing ARAM Lulu, and there was a Galio on the opposite team. I bought Mikael's Crucible to counter his ult, but it turns out you can't use it against him. The league wiki says his ult is a taunt and Crucible is suppose to remove all stuns, roots, taunts, fears, silences, and slows on allied champs.