All development is just re-solving or extending? That's a sweeping generalization. My own work is definitely the incremental kind, and maybe yours is too --- but surely you'd agree that someone, somewhere in the world is doing truly innovative work.
Well, of course you can. Pick any human endeavour, including software development, and I can demonstrate that it's just applied philosophy. But it's not a useful exercise, IMO, it's just a reductionist rhetorical device.
I think it's wise to keep ourselves humble -- few of us are blazing new trails, in anything that we do. And I agree that many so-called innovations are nothing of the sort. But if we reduce everything that we do to revision and extension, then the word "innovation" entirely loses meaning. Why would we want to do that?