If Apple's marketing were not key to its business why would they have spent over $1 billion on iPhone and iPad marketing since launching the devices (Google it)? Have you spoken with a teenager lately? Every single one of my younger siblings (1 in middle school, 2 in highschool) have an iPhone. They have an iPhone because their friends all have iPhones, because it's cool to have iPhones. They don't care about anything else.
So again, while your points are solid, discounting marketing all-together is very silly.
HP and Microsoft outspend Apple in Advertising every year. They should be doing much better than Apple if that is really the "key".
Apple's marketing budget relative to its size is quite tiny.
Is this remarkable to you because it seems like a big number? Or is it because this is actually a lot less than what their competitors spend? Samsung alone spent a lot more than Apple did last year on marketing and advertising. What do you think of that?