If studying composition and theory is necessary then I don't create music at all. All theory seems a lot of nonsense to me, and I could never see the point of any of it. Not that I didn't try. I took lessons from a prominent composer at one stage but the whole thing was a complete waste of time because in the end I still preferred my "wrong" sounds to his "right" ones.
Despite this, I have written hundreds of things and improvised thousands more recordings which say exactly what I wanted to say in every case. This imperative to create has been with me since I was a small boy.
Why do you want to create your own music ? Many people seem to do it because they are in love with the idea of composing, or being "a composer", rather than with the act itself. Some do it for fame, for money, for posterity or for a host of external and social reasons. The best ones just seem to have something in them which has to come out regardless of what they are taught or what happens in their lives.
Fugues, sonatas, or for that matter ragtime and blues, and all that old-fashioned stuff are neither necessary nor sufficient. Knowledge is never a waste, but in a peculiar sense it doesn't matter very much when it comes to mapping sounds onto your own psyche.
Quantum's advice is the best, as it often is. He has had ten thousand times my musical education but his improvisation has life because of something else entirely, not because he knows which chords Bach was likely to use. So heed what he says and just start to create, improvise and write following your own impulses and seek approval from no one.
If you want to create piano music, it does seem to be a fact that the best composers of piano music, old and modern, classical, jazz and everything else, were all marvellous improvisers. There has to be something significant in that.