why is it a tank meta again
why
why
Because all champions or at least all champion classes should be playable? What tank is meta? And if you say Mundo, he is a juggernaut. Not a tank.
There are few, if any, true tanks that are meta outside of support.
Most of the "tanks" you're seeing are juggernauts and fighters.
Really? No. Tanks are shit because armor is worthless. And true damage is rampant.
Only the juggernauts are terrifying atm

It is an all in meta. TTK is extremely low so the champs that have kill pressure and have some durability to survive the burst really shine.
what? its an assassin meta rn
ok why do they do more damage than ad aggro champs early then? why isnt their early game weak
The meta is great, everything is viable - including tanks. You have several strong tanks in every position aside from mid and adc.