In the absence of abusive advertising people would not suddenly stop spending money. They might even be more inclined to seek out new experiences without a constant mental assault by the largest corporations with the deepest coffers to bury them in their ads. Regardless of the way it goes, advertising is absolutely a net deficit to a small business - they don't have the capital resources or scale to permeate culture the way large corporations can. And if they are expending their limited resources trying to participate in the rat race they are sacrificing value to their existing customers and shortchanging their own growth for what is effectively an extortion of participation - if everyone else is deluged in manipulation to rob them and you don't participate there will be no money left over once the wallet has been rung dry by as many emotional vectors as possible for them to find you.
And with ads the mechanism is really obvious—-it helps people identify products that solve their problems.
The economy growing is not necessarily a good thing. For instance, the economy would get bigger if the government passed a law requiring everyone to buy mud pies — a mud pie industry would spring up, employ lots of people, and add to the country's GDP. But society wouldn't be better to live in for it, because mud pies are useless. Likewise, the economy would be smaller if people didn't constantly replace their clothes to keep up with the latest corporate-engineered fashion, or if they stopped buying books like Rich Guy's System for Making Guaranteed Free Money in Real Estate, but people would still be better off if they did.