I think your statement is not true.
Stuns/Knock-ups/Displacements Counter EVERY one equally.
Silences/Disarms Counter Specific Types of champions more than the other Silences counters Casters more than Disarms do, and vise versa for Disarming countering AA dependent type champions more than Silences.
And I would Argue that Snares counter mobile champions more than immobile champions, but Slows counter immobile champions more than mobile champions. (Example, snaring LB/Zed counters them harder than snaring Ashe. As it stops them from even casting a portion of their combos, where as Ashe can still cast her entire combo. Like wise slows would counter Ashe more than LB/Zed as they can still just dash into/away from as slows do not reduce the range of dashing.
Also your comparison is not accurate. Yes Stunnign kat IN HER ULT counters her harder than just randomly stunning a Taric. CCing counters harder when TIMED well (Kat in her ult). but if you randomly stun Kat like you Randomly stunned Taric then it counters them Equally.