That’s not true at all. Melee gets a free inherent 20% threat reduction. Mages/priests have to use talent points to get any threat reduction, while ele shamans, balance druids, hunters, and warlocks get zero.
https://www.wowhead.com/classic/guide/threat-overview-classic-wow#threat-modifier-abilities-and-values-warrior
The only reason you thought it was easier for melee to pull threat is because they were the only ones capable of doing enough damage in vanilla to pull threat.
And thats without even mentioning that for the only two ranged specs that get any threat reduction; spriests mind blast does double threat, rolling ignites are the worst threat hog in the game.
On to the next myth…