Where would we be without Mozart? Wow. that is an unusually difficult question. I would have to say that Classical music structure, as a whole, would be different. Mozart changed that face of Classical music by making it very simple in contrast to Baroque style music. He made it possible for the "common man" to commission music and claim ownership of it. 

I suppose if I really stretch it, I could even say that Mozart created a movement in which it was permissible for everyone to enjoy music and not just the aristocracy. 

This probably does not do your question justice, but it is as near as I can come to a solid answer.

Thanks for commenting on my essay.
Jill