. . . rather than its not right for their list or something?
If it was good enough they would want it wouldn't they? If there were a small problem they would be able to see past it wouldn't they? So does that mean its totally rubbish and no one would ever want it?
I find it hard to believe to they would pass up something genuinely good. Although you do hear these stories of published successful books having been turned down by multiple agents and publishers. But how rare is that?