when you see the other team is something like
and
I can't help but wonder if riot is ever going to give the players more than just
for tenacity cause once every champ on the other team has a stun 25% tenacity is just not going to cut it.
In season 2 Riot introcuded 3 items that granted Tenacity outside of Merc Treads. There was Moonflare Spellblade, Elise's Miracle, and Cloak and Dagger.
Those 3 items were latter removed from the game because nobody bought them, ever.
Granted: Tenacity was a unique passive on all 3 items and Merc Treads preventing any benefit from stacking them, but still: Boots offer such a low trade-off in build power if you really want Tenacity where major items offering Tenacity are, well, major items: and Tenacity just isn't worth giving up things like the Spell Shield on BV, the active of Zhonya's, the 250% crits from IE, or any other passive from a major item.
And really, if you're not going to give up something like 30% AS for Tenacity and 25 MR: what kind of item are you expecting to have available?
we need more tenacity with all the hard CC in the game
An important thing to mention with CC;
The vast majority of CC in LoL doesn't scale with item stats. With a physical-damage ability it goes up in damage with AD and down in damage with armor, but with CC: it's just a flat value regardless of what items are itemized for. CDR allows it to be a little more frequent, but there's no real counterweight to Tenacity if Tenacity were to become a stacking stat capable of making a wide range of CC effects less useful.
Also worth pointing out in regards to CC these items exist:

All of which can hypothetically reduce the duration of CC by 100%.
Finally: more Tenacity wouldn't prevent issues from running into chain-CC/mega-CC team-comps.
Out of all the CC these champions have: only Blitzcrank's 0.5 second silence is actually effected by Tenacity. "Airborne" effects (Grab, Fling, Knockup, Knockback) are completely unaffected by Tenacity, Tenacity reducing the duration of CC on yourself doesn't effect CC that's just applied when you're standing in a specific zone (like Singe'd mega-adhesive), and Tenacity has no effect on non-CC effects like the walls of J4, Anivia, and Trundle despite those having the potential to hamper your movement in much the same way several actual CC effects do.