Considering they cleared $2.6 billion on last year's Prime Day, and membership is up YOY, I'd say this comment is 100% knee-jerk/over analysing. Stuff breaks, things go wrong, planning for the worst sometimes isn't enough.
It is not a binary state of absolute destitute and top notch brilliance, it's a trend that can move one way or another and will show itself in more frequent outages, poorly rolled out products, lazy design and etc.
The plumping can keep on working for a few years even after it begins to erode. Historically there are many examples of this.