I agree that Amazon has dominated the retail market. But, as it grows, it becomes a bigger den of c-appy merchandise. Where, in the past, I rarely needed to return things, I find that I have a lot of returns now. The products from Amazon's "retailers" often are low quality as just about anyone can sell stuff through Amazon these days. The search engine brings up all sorts of junk when you want something simple. The user ratings are being inundated with people who get free or discounted merchandise for their reviews. Or there are plenty of fake reviews–you can tell they were run through Google translate and barely equate to English.
Amazon is at the beginning of its decline and is becoming a victim of size. And that's not a good thing if we lose other retail options.