If the book was any good someone would have published it by now.
Yes, probably. But maybe most of those agents I sent it to didn't even read it. Maybe it's too dark. Even worse it's not about celebrities. The hero is deeply flawed, maybe pathological. I don't think many women will sympathise either with his character or his predicament. Maybe it's dull, boring. Old-fashioned. Predictable. The happy ending isn't what it purports to be. It certainly isn't commercial.
And finally, yes, maybe it's crap.
At least this way you get to make up your own mind about it.