It is a myth many people and business owners have that if they have strong marketing, they will generate sales regardless of the quality of their products and services. The only way you can generate constant sales in a business while having average products and services is to spend too much money on marketing and the marketing will need to be ongoing which means that you will stop getting sales as soon as you stop marketing your products, which means your business won't generate organic sales which is what should happen after some time when you start marketing your business.
A business with good products and services will generate organic sales after some time. The reason behind that is that people who use your products and services will refer other people and recommend your products to them, and this continues as long as you are making good products and providing good services. With good marketing but bad products and services, your business will only stay afloat if you are constantly spending a large amount of money on your marketing campaigns to get new customers every time because you won't have recurring customers with those products.
I agree but even if people don't refer other people to a business to buy their products if a company is making good-quality products, they will still somehow get customers and they will also have recurring customers as you said because if I use a product and I like it, I don't find any reason to buy it from somewhere else or from another manufacturer when I know the one I used was amazing and I should get that one again if I need the same product in the future.
many businesses overlook this fact and you will see a decline in the quality of their products after some time. What often surprises me is to see some companies lowering the quality of the products that start selling very well, maybe because they want to reduce production costs and earn more profit but that is a very bad move as the product and the company loses credibility this way.