I'm glad you asked. Just two examples off the top of my head:

1. No timestamps on chat. Returning a product can require multiple chat sessions over the course of a week, where each representative swears on their mother's grave that in the next 48 hours we'll get an email and everything will be sorted out. They leave out timestamps so you can't clearly see that they've left you hanging for 15-20 minutes between each message.

2. Switching back to the recurring (vs. one-time) purchase option for some products each time you make a change to the order.

Numerous other issues, many of which are features that sellers exploit (mostly around reviews) and that Amazon isn't interested in fixing because they profit from those sales.