Answer:
In my opinion, marketing to everyone is not that effective; as the effective marketing activities should be targeted to the product's target group, or it will be waste of money.
For example, a marketing campaign of a rolls Royce car will be effective if targeted to the highest class of the market (upper class A, or what's known as "niche market"), but if targeted to everyone, that would be a huge waste of money to target people who are not my real customer, or potential customer.