I think we should bring back slavery
Why would you think that? Why does slavery need to come back?
It's because of the fast development of technology. The slaves are not human but they have similar physical functions.
I do realize that technology and machines are essential these days for modern development, but it's unfair to compare these past slaves as such things. They are human beings, not machines to be exploited. It's actually wonderful that we have machines to do all the menial things we don't want.
People should realize that slaves in the past were treated better than the people of today.
I think you should read some history books or find a nice documentary that delves into this topic. Slavery was abolished for a reason and I hope you can come to the realization as to why it was so wrong.