I mean, Walmart is also mega huge, and also allows 3rd party sellers on their website. is it troublesome that Walmart also promotes their own items or the items where they make the most profit first?
The other complaint seems to be "fairness." If you operate a platform, people expect it to be fair. But what is "fair" probably has more to do with historical cultural norms than actual abstract fairness, again it is the change the causes the issue. If Walmart started putting "see our generic option for cheaper over here" on end-caps that manufacture were paying top billing to place, they'd complain. But Walgreens has already been doing this in their OTC sections for years, just not with paid-to-place products.
As a consumer, I personally like the Amazon brands, because I can at least trust them to be real products with a reasonable quality expectation, not a switchout from some crappy seller or comingled inventory with fakes.
What irony. Amazon's co-mingling is actually benefitting them in ways other than lowering costs — It's actively driving people to their house brand(s).
Amazon is pure (evil?) genius.
I suspect Amazon just overreached. And not because of an intentional decision going sideways, but because of having many independent teams, with smart people, each optimizing for their own area. Frankly, it is actually amazing how much cohesiveness in action and strategy actually exists, as opposed to the mistakes we see (I'm looking at you AWS console).
Do note that this is all speculative anyway... There's been no ruling. Just some people pointing out problematic behaviour.
The anti-trust concerns would also apply to Walmart's own ecommerce. They're effectively leveraging their brick and mortar presence to establish their ecommerce business (which is presently the 2nd largest in the US). The 3rd largest is eBay, which leaves one to wonder how much of the hole left by Amazon would be absorbed by Walmart.