I have heard a lot of people say and believe that "if your product or service is good, it would sell itself". That's not entirely true.
No matter how good your product/services are, if people don't know about it or are not willing to patronize you, then you will have no customers or clients.
Try reviewing your response to what you heard people say about a product or service that is good, it will definitely sell. If after I examine the sentence it is true, of course the one who says the product or service is good is the consumer, meaning the product and service is already known. many people, as the saying goes "Excellent service, loyal customers". This reflects that the product or service is very popular with the public.