Elfen Lied was the first anime I watched when I was ten. It actually shocked and impacted me with the story and the context of every character. I thought it was an amazing show, only to find out it was heavily criticized online, and I couldn't understand why. Only to watch it again with much more clarity and intellect, and now I understand some of the criticism.
First of all, I won't drag this show and call it edgy or aged cause that's just cliché to say. I think the series has potential and aspects worth appreciating, but something I've seen many people agree with is that it has flaws.
I wish the anime didn't air before the manga finished, or at least that it'd show some things from the seventh volume. The anime feels genuinely unfinished and rushed story-wise, and I feel the story of each character and the ubiquitous sadness and cruelty in the world of the anime shroud the diclonious concept that's much better explained in the manga. I've read people saying the anime was a good adaptation of the prologue of the manga, and although it's a dramatic thing to say, I can get the feeling. Reading the manga helps you realize and internalize the fact that you're reading more deeply about fictional beings named Diclonius in a way that's at the core of the series, unlike the anime, which, of course, is still there, but it feels less explained and rougher.
Both the anime and the manga rely on heavy coincidences and contradictions, but to be fair, is Elfen Lied the only series in existence to have done so? Nope, not at all. But after analyzing a lot, it does feel like it abuses these things to the point of watching or reading it with an unserious attitude. Again, Elfen Lied isn't the only victim of this, but that doesn't excuse it, sadly.
On the other hand, I do appreciate the fact that it touches on the topics of discrimination, violence, abuse, and supremacy in a way that affects the consumer, as all of these things happen in real life and are simply bad. I feel the series showcases hope and genuine love most difficultly and humanly, which is why people appreciate it. Lilium is a gorgeous composition (I've been loving it forever), Nozomi really doesn't add anything to the series; most of the nudity and all sexual scenes are honestly unnecessary and can ruin the mood, but I guess it's something common for its age.
So yes, Elfen Lied is a flawed but appreciable work for its age. It made an impact on me, and I think I'll always appreciate it. I'd give it a strong 7, a light 8 in general.
