So there's been 14 posts on that site since Jan 2020. I clicked through a few of them, and it's things like someone complaining that their boss asked them to be a self-starter and get started on work without having to be explicitly told what to do. It's hard to take that seriously. There's one in there about being denied an MRI after getting injured, which doesn't sound ideal, but it's also only 3 sentence so I feel like I'm missing parts of the story.
And even if I did take all of these at face value and was outraged at them, an average of 3 complaints per month from a workforce of nearly 1 million is... well... makes it seem like Amazon is doing a stellar job treating its employees well if there are so few complaints. Of course in reality this website only captures a subset of employees, but just based on this site alone, my opinion has not changed.