Where in chazal or rishonim is there even a hint that slavery is a vedieved, or lo dibra torah etc type of arrangement? Tannaim had slaves. Tzadikim who are beyond the grasp of tzadikim who we ourselves can’t fathom, had slaves. If there were anything conceivably wrong with it, the tzadikim would not have done it.
There were rabbis who felt a need to say such things because goyim decided all of the sudden that everyone’s equal and that owning a person is evil, arbitrarily. But there’s zero foundation in chazal or rishonim for such an idea.
When we understand that Hashem owns everything, and that the purpose of this world isn’t material success, and that everyone is a slave to something, whether it’s Hashem, the yatzer hora, a boss, or whatever else – everyone is a slave. That’s also the name of a very good historical novel on the subject that mostly accurately depicts hashkofo on slavery.
Where does rav hirsch say that you can only get an eved kanaani from someone who’s already a slave? That’s not the din. The halacha is that any goy can sell themselves to a jew as an eved kanaani.