Actually, in that regard, it's because it's more successful that it is important not to dismiss the fans or ignore them. Because they are the driving force behind the success of the book. Yes, Marvel's not likely to cancel it if it dips in sales. But because of the name recognition of the protagonist, there is more pressure to do better in sales, and dipping from 80,000 comics sold a month to around 50,000 isn't exactly something Marvel probably is proud of. Especially when they market the change that preceded that dip in numbers as being necessary for the future success of the book.
When you are a franchise like Spider-Man's, with a large number of fans and supporters who have kept the book afloat and on top of the charts, that's not less incentive to ignore the fans. That's more incentive to listen to them, because you want to maintain that success.
To give you an example from my personal life, in regards to the percentage of sales in my company, only 20% of business is developed from new business. That means 80% of business for our company is return business. But that doesn't mean we ignore or not try to satisfy that 80% in pursuit of that 20%. We make sure that we treat that 80% right, because they can and will go somewhere else to get their product. The same thing is true with comics. People can and will go elsewhere for their product. So any sort of dip can't be regarded lightly.