Your point actually proves that, advertising gets the customer through the door, but, your product needs to be actually decent to keep the customer.You saw the advertisement, you bought the product and it worked as described, and continued to work in that way in the future.

The product is successful not because of advertising, because it is actually good. I find it weird that, most people spend huge on advertising, but sometimes neglect the product.

I have no idea. It’s rare I stain wood, I have never compared any other stain, I don’t know if it’s any good or not, or indeed the price. They may charge twice as much as bobs woodstain but it’s not worth me thinking about.

What you're describing is pretty typical though. You buy a product either because of advertising, because it "looked" like a good choice in the store for whatever reason, it was recommended on Wirecutter, the Home Depot worker or a contractor pointed you towards it, etc. And it seems to do the job and, for the amount you spend on that item annually, it's not really worth doing your own comparison which you probably aren't in a position to do scientifically anyway.

A lot of products are good though...So your point isn't very convincing that products aren't successful because of advertising given the zero sum game of hooking a customer for life that OP describes.