Current Amazon engineer here. People have been complaining working at Amazon for a long while.
At least in my organization, leadership pays close attention to whether folks are happy or unhappy in their roles. I posted this earlier, but we have a massive workforce of engineers at Amazon, across many countries. If 1% of them are unhappy, and even 5-10% of those unhappy folks are willing to say something about it online, you're going to see plenty of news sites picking up those articles and representing Amazon in a negative light.
There's plenty of bad publicity around Amazon, and I think that's due to the insane growth of this company. Regardless of your view, Amazon has been insanely successful. With that success comes suspicion, and you can quickly go from being very trusted to everyone questioning every practice – from quality of AWS documentation to Prime shipment speed to hiring/promotion practices, etc. Alot of people have skin in this game because they're competing directly with Amazon.
I'm not saying Amazon can't do better. We absolutely need to. But alot of the things being represented as systemic issues at Amazon are simply not so, but they certainly push a specific narrative. shrug