Gianni7, the real problem is stepping outside the boundaries of exercise and trying to create a work of art. It is not language or technique that creates it, but a series of things... which is a bit difficult to explain. You would only need to compare one of any work with your own little exercises to understand what I mean.
The topic of being self-taught seems abundantly exhausted to me... and if the great composers had a teacher, I don't see what's wrong with that. If it's an economic issue, okay... but if it were for principle, well... giving it up seems a bit limiting to me.