It goes without saying that you have to have a strategy and and good product.
However, even great product won’t be enough if you are not describing it well. There are many great products that died in infancy.
As for product that sells itself, i think Drucker was stretching this idea. Amazing product not necessarily leads to success and growth.
Take Slack for example, probably the most successful enterprise product in generation and look how well and how careful they were from the beginning about messaging, positioning, and PR.