Umm . . . yes, but they're also practically always evil (except Large Luigi and Gnome Ceremorphs, I guess). There's no problem with having them enslave others and experiment on them, because they're almost always the villains.
I seriously can't see what the problem is here. And I'm one of the posters on this site that has been for every pro-inclusivity change discussed at length on this site in the past couple of years. Removing Aberrations is not that, and having Neogi, Illithids, and Aboleths be slaves isn't a bad thing.
(I mentioned that in my last post, when I said that it could be argued that the Mind Flayers are stand-ins for white supremacists/imperialists, and maybe fascists. They're a world-conquering species with superior technology to those that they're conquering, commit eugenics on their thralls and themselves, oppress the religions of their subjects, are extremely racist, and completely obey every command of their colony leaders. If they're a stand-in for anyone, it's imperialists/white supremacists/fascists.)