Fair enough. I could've expressed myself better, because i'm not denying effort that he puts in what he's doing. But when push comes to shove, the thing that the guy cares most about is working (in literal sense). There's little to no progression in terms of changing the status quo or character development in his long running series (not when you consider the publication timespan, where those miniscule alterations can be attributed to aging), because that would mean coming closer to a conclusion, and that in turn would mean "no work in the future". As a western counterpart i offer you Mignola and his Hellboy universe. Is he dragging things out and milking the franchise? Sure. But along the way, stuff is happening, landscapes are changing, and characters are evolving or they die trying. Aoyama on the other hand, is interested, more or less, in doing the same thing over and over again*, at least from what i'm seeing. There may be set quality to that thing, but i wouldn't exactly call it "caring", not in a sense that i presented above.
That perspective of course, may be projecting on my part, because i don't have access to what's in Aoyama's head. It's just an impression that i got from reading his stuff (up to a point, i no longer do), but an impression that i do feel strongly about.
I hope that explains things to you both, and if not, i'm sorry. That's probably most clear i can be, given that writing this relatively short reply (combined with editing) took me about 20 minutes.
*Then again, he's putting out other stuff, so calling him dull or stagnant (as an artist) would be an overstatement. But we're talking about specific series here.