what else are they? Indentured? i dont think they were volunteering.
I dont see the point in debating the semantics.
also
>aztecs were pretty small
Only if Rome was very small too.
Every empire was that, a small core dominating a large region by conquest.

also
>Industrial scale
i never realy see how it not beeing on an industrial scale makes it any better realy.
If you lived in italy and Arab slave traders enslaved your entire village you probably didnt give a shit about it beein "Industrial" or not.
You mean because the perpetrators didnt give a shit? I dont think they ever did regardless.
The consequences for the victim are the point that matters as far as im concerned.

>Real world inspiraiton
The first Art Humans invented was the grand art of Remixing.
And realy they never invented any other form of it.

So i wouldnt call that a surprise.
>unintentonally beeing offensive
i dont think anyone is intentionally offensive when making a fantasy setting.

If youre offended, chances are its your own fault. Theres no fixed characteristic which determines what you can or cannot be offended by.
Hence why i say: why bother. Theres no reason even attempting to be inoffensive when what is and isnt offensive varies by an individual basis.