To be fair, I perfectly understand where OP is coming from.
You see, guys, 5/10 rating is supposed to represent a "normal" "run-of-the-mill" title. Average, even. Meaning, if you somewhat enjoyed the manga, but didn't find anything special about it, then, objectively, it would be 5/10. Like a TV show: "how was it? It was all right." We're not even taking into account the fact that "enjoyment" is but a part of the overall score, others include things like "art," "story," "characters," "value," (which, arguably, is something one can score only with a lot of finished titles and a knowledge about the overall industry and it's history) and so forth.
What happens, though, and, actually, what has always been happening to any DB with a score system, is that most people rate a title 10/10 if they really liked it, rate it 1/10 if they hated it, even if it's just the ending that they didn't like, and don't even comprehend why is there anything below 5, basically never using 2-6 scores.
I think the only sole exception from this inherently dead system where people with no idea about objective criticism of artwork, none whatsoever analytical skills, and at best a few dozen finished titles at their back are given the ability to rate a work 1-10, is AniDB, which actually has a lot of things rated between 4-5, which is remarkably sane, considering the over-saturation of the market, abundance of fan service shows and the lack of talent in the industry. Can't say for MangaUpdates, though. They are fair, but the overall user count is so meager, that you can't really grasp the overall idea since even popular titles won't have more than a few hundred scores.
What I mean by this, OP, is that you're asking a community of people that don't even ever think about objectiveness, analysis and comparison, to give out fare scores. And you can hardly blame them, since most of otaku just watch fan-service shit, never bother much with even just seinen works, have never heard of LoGH, and think that Eva is the top that anime has to offer, actually not even getting a fraction of this title's message.
Just give up. ThatAnimeSnob couldn't enlighten this system. Why can you. Though, he's as much of an asshole as he is a great analyst.