1) Paid advertising is obliterating natural search results. Natural search results lead to greater customer satisfaction, paid search leads to greater corporate satisfaction.
2) Fake reviews are destroying much of the value of amazon reviews. Additionally, using a simple average of total reviews is not optimal. Bad reviews should be weighted much more than good reviews. Emphasis should also be placed on the distribution of reviews which is more informative than the mean value.
3) Counterfeit items and the lack of a genuine guarantee leads to a lack of trust in the online marketplace. Often people prefer to pick up items from local store as they can be assured they are not counterfeit.
4) Why is it so hard to find a good pair of sheets on amazon?
One thing Amazon really needs is a way to search for a product with a specific size/weight/<other property> range. Search for "3 inch screw" and you'll get screws of all sizes. Another bad thing Amazon has started doing is throwing random products into the search results. Search for pillow cases and you also get a bicycle and shoes in the search results. The review weightings were changed some years ago to make the "average" higher also, it's no longer really an average, especially when the lowest review score is one instead of zero.
After the pandemic messed up it's algorithms Amazon never really recovered and search results have gotten really weird. There are many obvious examples of price gouging as well. It really seems like Amazon is now selling us to the products, rather than selling the products to us. And why on earth does Amazon still (after many years of doing this) list products that are not available? I can understand keeping the pages active for previous buyers, but a search for a product should not turn up hundreds of hits for things that are not actually available. Additionally, instead of returning only items that match my keywords, I often find that two or three pages into the search results the products listed don't match ANY of my keywords, and there will be 20 pages of them; they are adding hundreds of products at the end of search results that could not possibly be relate to what I'm looking for, just to try to sell me _something_.