Fascinating! Recently I've been falling in love with Prolog and it's possibilities particularly when it's fast and embedded in a Lisp.
Prolog as a culture is amazing; the depth of it, specially when it's submerged in other disciplines, like constraint logic programming.
But, standalone, as a language, by itself: it either forces your problem into a text-book toy exercise, or drives you to frustration. It does all the difficult stuff out of the box, but you will need to cut through it with a machete to accomplish the mundane.
I suspect that you have just used the wrong tool for the job. Prolog works well for problems that require reasoning, and unification extensively. But if you are trying to write, say, a parameter estimator in Prolog, you are using the wrong tool for the job.