it sounds like a joke but that’s their original purpose

the hatian ‘voodoo doll’ was based off of african healing dolls made of wood. you would do nice things to the doll, place it in nice places, or add brightly colored pegs. you made dolls of you and your friends so you could try and make their lives comfortable

the one we think of was corrupted by the brittish, who had ‘poppets’, which were fabric stuffed dolls you stabbed.

It’s way shittier than that. European poppets and the various types of African spiritual effigy were both originally intended to be used to heal someone or cast spells on them via sympathetic magic. The idea of using a “voodoo doll” or similar effigy to harm someone only really came about in the 20th century, seemingly for no other reason than making African religions seem more sinister (never mind that European “cunning folk” historically utilized poppets even more often).

As far as actual Haitian Vodou goes, there is no such tradition as the “voodoo doll”, and anyone who tells you otherwise is probably trying to sell you something.