As you can see, the plot sure sounds simple, the animation looks childish, to be honest I thought it was childish too AT FIRST. A lot of people don't give this anime a chance. Probably because of how it looks. When you see Naruto, you see a ninja. But when you see Hunter X Hunter, you see a couple of kids. And people don't know that they're badass. Anyways, that's not the point. This anime is underrated because it's too psychological, varied, and complex for a regular shounen fan.
I highly recommend this anime if you like an actual planned out anime, love FMAB, no filler episodes, an outstanding soundtrack, several amazing arcs, f***ing AMAZING character development, good quality animations, and a catchy opening.
To me this anime is a masterpiece. Give this Anime a chance.