I won't lie I'm a bronze
The win rates for champions are actually pretty much the same from Bronze up to Diamond. Once you hit ranked most players at least get the basics and you can be successful with any class.
Might as well just run with whatever suits your fancy.
Also - there's 2 very different play-styles with a full tank champion, namely there are:
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tanks, tank/supports, tanky CC
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fighter/tanks, tanky DPS
Tanky CC champions are among the best team-fighters in the game. Inversely pretty shit in a 1v1.
Tanky DPS are among the best duelists, and inversely among the worst team-fighters.
If you want to run a lone wolf, solo-carry mentality, fighter/tanks are one of the best archetypes to run with.
They often do crazy damage in full-tank builds too, so it's not like full tank means no damage.
That's more true in turn-based games where you don't have the survival tools of range and speed to balance a game around. In LoL, tankyness is often one of many tools to survive long enough to get a job done, resulting in tanky DPS champions like Nasus to stay pretty even with mega-ranged champions like Ziggs or incredibly mobile champions like Zed in terms of damage inflicted.
Also - I've had really good experiences with fullfilling supportive rolls in Bronze, and actually shot out of their pretty fast when I decided to use Leona rather than trying to carry my team with the damages.
If you're running into a full late-game, no support, all kill-based, lone-wolf team as a tanky CC champion, you can defeat them pretty easily, exploiting them early, exploiting their lack of support, exploiting their poor formation choices, exploiting their lack of initiation. You get a massive strategic edge with a tanky CC champion more often than not, it's all about using it effectively. Which can mean being pretty chatty, especially in champ select to get communication flowing.
In either case - it's more about your own mentality.