Illaoi is a bruiser, not a tank. She deals crap tons of damage with high sustain but is actually fairly squishy save for her high hp.
Braum is a support tank, he deals no damage but has massive utility.
Tahm is a juggernaut... kinda, he doesn't really do damage till he hits 6 but you typically won't be building items that allow him to do lots of damage anyway so, he's more of a tank but pretty much he's just better off as a support tank.
Zac was the last true tank to be released, before him it was darius.. then hecarim, naut, sej, voli... you get it... it has been a while. One of the big issues with getting a new tank is that the current meta of the game is 'whats a tank?' so if we were to get one, it would be freakishly tanky in an actual tank meta season.