I mean- hand a person a gun, and they might shoot themselves in the foot. While you can make bad queries/workloads for a relational database, you can just as easily make bad workloads for DynamoDB.
This is underrated, but it's really helpful. So many times w/ a relational database, I've had to tweak queries or access patterns over time as response times degrade. DynamoDB basically doesn't have that unless you really screw something up.
For me, I like that 98% of DynamoDB work is frontloaded. I spend the time building the model but once it's done -- set it and forget it.
With RDBMS, it's like there's a hidden 5% tax that's lurking at all times. You have to spend time tuning querying, reshaping data, changing patterns, etc. It can add up to significant drag over time.
Different teams might think the costs are different for their application, or they may be fine with one pattern over the other. Fine with me! I just know which one I choose now :)