This article does not make convincing arguments to match the strong criticism. Engineering decisions are difficult, especially in high-growth orgs, where one must balance many constraints and risks including opportunity cost. Handling payments is part of Uber's core product.

The financial criticism ('napkin math') appears to estimate DynamoDB costs of USD $8 million for 2017 to 2020. Uber revenue for the same period is roughly USD $42.5 billion, thus this cost weighs in at about 0.02%, or 1/50th of one percent. This is a rounding error for a high growth company, and not something that warrants a witch-hunt and firing. It's easy to blow more than $2 million per year on software engineers in pursuit of an alternative high-scalability solution.

I'm also not on board with the 'resume driven development' criticism as the explanation for solution churn. Perhaps that is actually what happened. I wasn't there and don't know, but if that is being asserted I expect to see evidence presented to support it.