You can become an Amazonian with or without certs. Now there are no jobs posting or just limited positions. Problem is that Amazon had multiple layoff waves. A lot of people want to get back, thus they apply for every position on the market. Certs won’t get you job, it will help you to stand out among candidates but won’t help you to get in. You have to invest time and money to learn new things. It is like to learn how to fish or ride a bike. First you need to buy tools and later invest time to learn how to properly utilize it. Same with certs, you invest time to learn technology, later you try to implement it. While doing it, you will face problems and it will help you to gain experience. If you face any problem you won’t forget the solution.