It’s a problem because the small sellers take the financial risk trying to sell a new product, then when Amazon sees it’s doing well they make the clone and get the profits.
They can't have it both ways.
To illsutrate my point, please take a look at the results: https://www.google.com/search?q=site%3Anews.ycombinator.com+...
I think it indicates a deeper problem, either on how we perceive these companies, or how Amazon succeeded in making itself look like a random traditional company. I don't know the solution outside a very prominent decade lasting lawsuit we could all point at, the same way we had the Microsoft antitrust lawsuit decades before.