And magic can make up for the need for slavery as well.
Slavery has never stemmed from a "need", so this is some misguided stuff, dude.
Slavery is about power and avoiding costs.
Magic could help, but not in the "replacing the 'need' for slaves", because slaves are never 'needed'. It could help by making it nearly impossible to enslave people long-term because magic/the gods keep freeing them. Especially if people can access divine magic through prayer, or develop powers internally or the like (psionics, sorcerer) or talk to third parties and gain powers (warlocks, etc.), slavery might well not work very well.
And you still don't understand that reducing something that has harmed, and continues to harm, millions of people to a fun pastime may be something that major companies don't want to do?
This is a very weak argument AND as a bonus profoundly misunderstands why companies avoid slavery.
By that logic, the colonial/imperial attitudes present in the vast majority of RPGs should be done away with - and maybe they should be - but D&D's entire "kill things and take their stuff" is reliant on that. Further, violence should be excised from RPGs. Violence is a much bigger problem than slavery, right now, in the world. It's likely to continue to be that way for a very long time. Most RPGs absolutely glamourize violence of almost every possible form - physical, mental, magical, cultural (some argue sexual re: VtM etc.). Far more people worldwide have bad real experiences of violence than slavery.
And before you try any "whataboutery" nonsense, let's be clear, special pleading re: slavery is itself dubious. This whole thread is about "controversial content".
Anyway, the real reason slavery is avoided at the moment in RPGs has nothing to do with real sensitivity to the issue, nor to do with it harming people today. It has entirely to do with the fact that US chattel slavery was particularly vile, even compared to other forms of slavery, and only ended relatively recently, and the US as a country, has miserably and completely failed to deal with the consequences of that, so it's very much a live issue in the US. That is really the primary driver. I don't know if you don't know that, or don't want to face it, but that's what it's about.
It's also notable that this is solely a TTRPG thing, other media
absolutely is not following that rule and never will, I would suggest (one possible exception being YA novels, but that's because that's a bizarre environment with its own rules and conflicts). So there's always going to be a kind of messed-up deal where you can watch heroic characters kill slavers and the like on screen, but the game you run an hour later, it's inappropriate for you to feature that.
The funny thing is, I don't entirely disagree the full-on slavery, especially not US-style chattel slavery is best left out of most games. It's not going to be handled well. But the arguments you're deploying are specious.