Does Mikael's crucible stop suppresses as well, when used? It wasn't in the description of the item, but almost every other debuff is.
Crucible does not remove Suppresses.
Check the wiki for Quicksilver Sash. It says it removes ALL DEBUFFs and goes on to explain that it includes Suppresses.
Mikael's Crucible however does not say ALL DEBUFFs, instead it states the debuffs that it removes (stuns, roots, taunts, fears, silences and slows). It's a thin line but you can see the difference.
I think it's the same for summoner spell cleanse (where it doesn't say all debuffs either) because it doesn't remove suppress either.