It replaces the DBA for routine maintenance. It does not replace the DBA when you need an expert to help you plan your database architecture and figure out what went wrong in production.
As compute get cheaper, the design goal of those new systems is to replace human time with computation time. This is the key idea behind automatic machine learning, for example.
Image a system that needs to map logical schema or architecture into the best implementation. The system can create 1000's of combinations, and test them against your data/queries. And come up with the best design.
It replaces the DBA for routine maintenance. It does not replace the DBA when you need an expert to help you plan your database architecture and figure out what went wrong in production.