Faolyn
(she/her)
It really depends on if the DM wants there to be Cosmic Good and Cosmic Evil (or Cosmic Law and Cosmic Chaos). If the DM does, then differentiating between evil and Evil is useful for the conflicts in that game. Mind Flayers may very well have a role in one of those sides.That's my question too.
What is the value of calling the brain-eating monsters evil?
Their very existence is antagonistic to our own. Where humans and illithids meet, there WILL be conflict.
What is the point of adding the artificial conflict of Good vs Evil when you already have predator and prey?
If the DM doesn't want there to be Comsic Alignments, then as you say, the conflict is between predator and prey. With the added bonus of mind flayers not evolving in the game world's reality (usually, at least) and therefore being not only a predator, but a dangerous invasive species as well.