AoE tanking wasn't a thing (you'd use CC on multi-mob pulls and only fight 1 mob at a time most of the time) and only the warrior had a full kit of tanking abilities. Sunder Armor was the best threat generator bar none, they had a taunt, I think they had an aoe taunt on a long CD, they had hamstring (mobs running away would wipe you if they got far), I think they had shield wall back then too.
Classic had a different design ethos. Each class had a specific, unique role and had unique utility to support that role. So it was natural that there was a 'tank' class. Other classes could sort of tank (Paladins, Druids, even Shamans) but you brought them along for their supporting abilities and in that role they were all fantastic offtanks if spec'd appropriately.