Tenacity is a Lose More stat

Wait until you've played thousands of games and got hard locked in place by conventional roots and stuns for 6 seconds.

There's several Hard CC's Tenacity actually multiplicatively reduces their durations btw..... so when you have 51% Tenacity, some skills will have an effective 76% reduction in their duration. This includes several slows, Ornn's Brittle, and some roots.

The only time you do not need tenacity is when every champ's major cc on the team versus you is a knockup/down/displacement. Otherwise... it's a godsend.

Inb4 all the new champions just get free cc unaffected by Tenacity for literally no reason:

It's just situational.

In a teamfight if you are a squishy champ and get hit by a stun chances are there will be followup CC and enough burst that reducing any of that CC doesn't matter.

But if you are a tank or bruiser chances are you can do something with any window of time there is between chained CC. Tenacity can potentially open up small windows in between CC that otherwise would be perfectly chained.

If you are against champs with long range CC like Morg or Lux, Tenacity can reduce the window of time that the CC creates for the enemy team to follow up and actually catch you. But against Lux if you're a squishy champ you'll just die to her ult anyway so it still might not necessarily be useful in that situation.

So you have to ask yourself, if I have tenacity, specifically how will it help in actual situations I will be in, given the enemy champs and my champ?