Twenty years ago you could have an average product and make a good living. Now competition is global and there is an online middleman that is making a profit from all industries and niches imaginable: Google.
If you depend on paid traffic from Google or other sources you have a problem. Traffic is sold to the highest bidder and this creates a race to the bottom. At some point somebody will be willing to take a smaller margin than you.
The only way you can compete in the long-term is by standing out. You have to do something that is so good that people will seek you out and come to you.