It probably is, but maybe it'll do better later on the story. I'm liking it as well but I imagine that the fact that the manga is so slow in building the story and the pacing is as well, the readers maybe are not enjoying it as manga on WSJ are generally faster in pacing. I saw similar complaints in the west as well from the people that didn't like it.
Anyway, like you, i'm cheering for it doing well.
One of the reason why I like The Last Saiyuki is because it's a slow burn and doesn't go at a crazy fast pace. But that probably is the reason why it's doing so poorly. I do hope that it does start to gain more traction soon enough.