Rammus in this Tank Meta
Before cinderhulk in the land of assassins,
was extremely strong. He could survive any assassin's burst, and taunt them for an easy kill. Him jumping on an ADC is pretty much a guaranteed half healthed if not more carry. Most enemies didn't have the peel necessary to keep him off of the team.
However, with the new tank meta, he's suddenly much worse off. Since he has no %hp scalings of any kind, he's very weak at fighting other tanks. He has respectable base damages, but nothing enough to chunk his brethren. So most tanks can output more damage to tanks than him. Before the meta shifted though, this wasn't too big of a deal, as you only had to deal with at most 1 tank on a team. Now that there's so much more peel and tankiness on the enemy team,
can't do his job. He can no longer CC the enemy assassin/mage, as there's this brick wall he can't get past. His only mobility is literally body blocked by them. His damage is ignored by them. Yes, he can always do damage to the ADCs, whom he counters, but with so much more meat there, he just can't get over there.
And thus the meta shifts away from my favorite champion, ironically in a "tank meta".