DynamoDB has basically two legitimate use-cases that I'm familiar with:

1. You're selling a system to a customer to use within their own AWS account, that you will have no access to, and it needs a transactional datastore (not just an object bucket) of some kind. The fact that it costs nothing by default (particularly valuable when the customer is trying to deploy a proof-of-concept), scales more-or-less perfectly without anybody touching it, requires zero day-to-day maintenance by you or the customer, and all it will ever ask is that you throw money at it, is very, very much a feature. One example I'm familiar with in the wild is Teleport: https://goteleport.com/docs/reference/deployment/backends/#d...

2. You have a huge OLTP workload that fits Dynamo's KV patterns (e.g. Amazon.com shopping carts, which is what it was originally built for). You don't care how much DynamoDB costs (in either dollars or engineering limitations) because any alternative would melt your face off if you even tried.

Most of the pain that comes from Dynamo is people who try to use it as a primary datastore in place of a relational database just to get the serverless pricing model. It's not worth giving up the flexibility on greenfield systems. It does become worth it to give up the flexibility when your system is mature and you don't have genuine flexibility anymore anyway.