I dropped this series but still gave it a 7, because the first half of the manga was so entertaining that I originally wanted to give it an 8 (maybe even a 9 on a good day). I would feel wrong if I gave it a 6 or under, because the series did offer me significant entertainment.
However, as the series progresses through significant climaxes, the author seems to snap: it feels like they decided to bypass their original ending and thus continued to make a series without the flexibility or creativity that is needed to make late game scenarios entertaining. Nobody wants to read a series that repeats the same ending to each arc over and over again, but here we are; that's what happened in this series..
If it had ended at a certain point, I would have loved it, so my head cannon has decided that the newer chapters don't exist.
I would normally go into more detail about the art and whatnot, but I've said my piece: If you're willing to accept that the series runs too long and you'll stop enjoying it eventually, then please read this, because it's really good up to a point. If you can't do that, don't read this.