> Then, one day a new toaster comes out, and it might be even better than the old best-seller. How would it get sufficient traction to be recommended by the algorithm?

This is a solved problem. Recommendation algorithms aren't just "highest average rating", they take into account number of ratings, recent trends, etc.

Even if some ads improve this experience, Amazon is orders of magnitude past that threshold into hostility and toxicity. You have to scroll through pages of sponsored results to find anything worthwhile.