Faolyn
(she/her)
It would be better.How much more would they need to add to meet your requirement of, "showed the impacts of slavery"? Your complaint was that the slaves had no identities. If they had the same degree and proportion of identity as the other NPCs in the module, would that work for you?
Again, I bring up Spire, a game that shows how much slavery messes people up, in comparison to D&D, where you could literally replace the slaves with cheeseburgers for all that the slavery actually matters for the worldbuilding. So why even have the slavery in the first place? It can't be because it makes the game more interesting because it doesn't. It does nothing more than say "those guys over there are the bad guys." It doesn't make the game more mature because it doesn't do anything with the slavery that's mature. It doesn't show realism because the hopefully-soon-to-be-ex-slaves aren't treated as people, just goals. Slave Lords apparently didn't even assume the PCs would care enough about the slaves to ask them their names. The slaves were nothing more than MacGuffins.
This is a major reason why many of us are against including slavery and bigotry in the games. D&D, and indeed many other games, doesn't treat it as any more than a plot hook.
You and others have said that bigotry is great in the games because it brings up conflict. OK, like what? Do you actually make sure to have people discriminate against those PCs who chose the wrong race/sex/skin color/whatever at game start? Do you throw them out of taverns: "we don't serve your kind here"? Do you have the watch just automatically assume that the half-whatever or full orc or whomever is guilty because of course half-whatevers and orcs are the bad guys and go out of their way to hassle them? Do the other players treat those characters poorly and say things like "you may be a half-orc, but you're OK"? Do you go out of your way to make sure that PCs who are playing an oppressed minority feel every minute of that oppression, the way actual people are discriminated against?
Because I'm going to guess that for most tables that assume bigotry is great for games, nothing like this happens, or is used specifically by jerks to harass a particular player, or is simply used as an excuse: you can kill those orcs; they're evil.