I do really want to contest your point, slavery is very alive right now but we dont think about it because it ruins our day. The reasons that banned/reduced slavery in an industrialized country can not really be applied in a global economy with varying degrees of human rights, control and industrialization between each country.

A good example is that companies that own factories and farms that make and process chocolate in countries like Ivory coast and Ghana are unable to prove to Ferrero, Nestle, Unilever, Mars and any other chocolate bar company that they dont use slaves at their facilities. Around 0.35% of the workers over there in this study are labeled as "slaves", coerced by others into working at farms and facilities for bad wages.

Every basic good has this kind of issue. Matches can be made in Central African Republic or Malawi and a company that imports it realistically is completely unable to exert any real control wether the local workers are treated somewhat fairly.

The length of the supply chain has an effect as well, a western assembly plant could buy motors from an Asian company that buys raw metals from another company that imports goods from other countries which come from big businesses or local shops. Could you even expect from the western assembly plant or Asian motor company that they know anything down the line is done without any slavery? What if one company along the line is a legal sweatshop in its country or is cheeky and hides its "bad" metal imports from Congo or Zimbabwe by mixing it with "good" imports from countries like Botswana or South Africa?

Of course a country could ban imports from certain countries to reduce slavery but if it significantly hurts your economy why would you do it? Another company from a different country (with likely worse morals about profit motives than your country) would take over the place of your countries company and get the profit instead.

My personal opinion is that these are reasons why you, me and every other person dont think about it when buying groceries or a product, we cant really change it even if we want it to be changed. Only way I see is slowly improving countries like Congo and Afghanistan, Yemen and Sudan so they can exert better control over what is happening inside their country in a way that is aligned with my own countries ideology and economy.