William Joel has a style that derives heavily from other composers, which means they are influences on his work. Its hard to listen to a Joel piece and say, Oh, thats Joel! In other words, he hasnt as yet formed a personal style. That comes with musical maturity. Early Beethoven pieces are heavily indebted to Haydn and Mozart, particularly the chamber works, so there is no shame in this. Give him time. This sounds a bit like Debussy, Rachmaninov and Scriabin, thrown together with movie composer Bernard Hermann.
Joel: Fantasy (Film Noir), Op. 4