Lots of ways. Directly, such as - https://www.wsj.com/articles/amazon-scooped-up-data-from-its.... It's a marketplace for laundering counterfeit and knockoff goods, harming the interests of legitimate businesses. Also indirectly by creating market pressures around logistics, pricing, SEO, and paid advertising that make it very difficult for a small operator to succeed against. A small business can struggle against a vertically integrated giant like Amazon, but only a very small portion will succeed to any degree.
Moreover, it's incredibly frustrating, as a merchant, dealing with an unregulated private bureaucracy like Amazon's. I know plenty of merchants who have had their inventory mixed with counterfeit competitors, received arbitrary account bans (including having funds frozen), and had to spend large amount of cash to comply with new policies that they invent with little warning.
None of those are barriers. If you want to live on the amazon platform, you end up being a serf on their platform. That's a given.
If you want to start a small business to compete with amazon, then of course their logistics, pricing and SEO is better than you. That's like saying that you want to start a garage car manufacturing plant, but you are out-competed by automanufacturer's investment in robotization and automation, and streamlined inventory management.
That's not a 'barrier' per se - it's the point of amazon. As a small operator, if you do not have a value proposition, you don't have the right to exist.
So are the barriers to entry obvious or nonexistent? Because you described both. Not only are they barriers, but vertically integrated monopolies have been illegal for a century. If erecting economic moats is the entire point of Amazon like you said, then it’s obvious they need to be broken up.
You really don’t think small, independent merchants are affected by Amazon’s 2 day delivery or taking back any return? That’s naive.
Moreover, it's incredibly frustrating, as a merchant, dealing with an unregulated private bureaucracy like Amazon's. I know plenty of merchants who have had their inventory mixed with counterfeit competitors, received arbitrary account bans (including having funds frozen), and had to spend large amount of cash to comply with new policies that they invent with little warning.