As for the profound part - what I'm about to say should not be taken as a personal attack but as something that should give the potential viewer a general idea of what Elfen Lied is about - this title seems like it was written by a person resentful of the rest of the world. Maybe not in an edgy way, as in it's not straight up presenting humans as the supervillains of the whole show but rather in a self-depreciating manner.
I think there is nothing wrong with showing humanity and its core tenets in bad light, in fact my favorite artworks are doing just that. However I do think - and that's where the "harem part" comes into play - that mixing tits and ass with a little bit of romance does not do any good for a plot centered around moralizing, psychological themes and slaughter. It just doesn't.
Depending on how you look at Elfen Lied it might be an interesting anime with really good character development or a huge mess with inconsistent story fueled by cheap tricks meant to squeeze some tears out of the viewers and... I guess feel bad about themselves.
Overall I think it would not be fair to rate it below 3. I'm giving it a 4 because it was not bad enough to make me laugh at every attempt it made at invoking emotions but it was also not good enough to make me care about... Whatever its message was supposed to be. It did make me think about possible reasons for how someone would come up with such a grim plot though.
For a psychological story this one certainly isn't compelling nor relatable. But it's not unsalvageable either.
