I don't want an open marketplace. I want somewhere I can conveniently find most things I need from my laptop for a reasonable price.
If Amazon came alone with insane, draconian policies and made it a very closed market, I'd be ok with that as a consumer so long as I can find what I need.
They don't have the range of products you can find on Amazon. If Amazon is supposed to replace Wal-Mart then they need to sell the same range of stuff - and with a certain minimum quality standard.
Anecdotally, 4 or 5 years ago I used to go to Amazon to shop with only a "general idea" of what I wanted to purchase. There were many times when I ended up buying more than I wanted, or something more expensive than I originally intended, because I was influenced by reviews and how the items were presented to me on that site (like "People also bought..." listings).
But after getting burned a few times with products that did not live up to the standards presented in bogus reviews or product rankings, now I only use Amazon for the fast shipping. Instead of spending the majority of my time on Amazon doing the research there, I'm spending it on blog posts, reddit, or YouTube looking at real testimonials and going to Amazon only when my shopping is already done. Those extraneous checkout-line addons are no more.
In this way, Amazon definitely does itself a disservice by (seemingly) shifting their priorities away from what they used to excel at to more "big picture" ideas.
If they can control ever growing swathes of the world's economy, they are not doing themselves a disservice. Maybe they are giving you less service than before, but they are simply doing what big companies do.
Again I said it was anecdotal, meaning that it was just a story that illustrates a point that the parent comments were making. But for fun I decided to look at my order history and found that from 2013 to 2014 the money I spent on Amazon dropped 55%, and from 2014 to 2015 it dropped 86%.
I'm only one customer, but clearly I'm not the only one with a growing frustration, and this case (since that's the only one I can attest to) they're losing real money, and I would cause that a disservice.
Unless either 2014 or 2015 had a negative total, you did the math badly wrong on that "dropped 622%" line (most likely by using the end year rather than the start year as the base.)
But if they are making more money overall being a crappier online store, they are only doing you a disservice, whereas their shareholders would be happy.
If Amazon came alone with insane, draconian policies and made it a very closed market, I'd be ok with that as a consumer so long as I can find what I need.