If it seems like "everything's been done" try mixing styles to make something new. Look at Western Swing (in the 30's, somebody asks "what'll happen if we put together hillbilly fiddle music and horn-based swing jazz?" - only in Texas). Look at Ry Cooder in the 70's, using Flaco Jiminez and his San Antonio conjunto for instrumentation and 3 gospel/r&b/soul singers for vocals and his slide guitar pulling it all together to create what? - TexMex SoulBlues Rock?. In fact it might be possible to make a case for saying that the major changes in popular music in the 20th century were mostly if not all from juxtaposing different styles in a new way. And the guitar took over from the piano as the instrument in everybody's homes (starting in the mid-50's i think) because it was more mobile (& cheaper, but it had always been around in poor houses). Maybe the guitar became the dominant instrument just because it was so accessible, 'democratic' & portable.
But i start to ramble; i didn't read the whole thread, just jumped in when a comment about it all having been done hit my scanning eye.