Cleanse isn't good for "certain kinds of CC," it's good for all of them except suppression, which can only be stopped by interrupting the champion applying it. It also gives you 65% Tenacity for 3 seconds, meaning any disables (again except suppression) being applied afterward have their duration completely trashed. Further, it removes things like
, and has the same cooldown as it, so you can really screw champions like
that tend to Charm > Ignite for all-ins.
Clarity, meanwhile — restores some mana. Controlling your ability usage and mana consumption is an integral part of improving at the game, and Clarity, frankly, just encouraged people to keep being bad at it and not improve. It warped the ability to balance base mana and mana regeneration. It's useful in Twisted Treeline where recalling isn't a thing, but that's it.