It’s two different approaches to the same problem. Given the problem “the business layer wants to do X, and that’s inefficient in storage layer Y”, DevOps engineers solve the problem by adding another storage-layer component Z that follows a paradigm where the queries from X are “automatically” efficient; while DBAs solve the problem by informing the design of the business layer to make queries that are optimal given the storage layer in use.

For example, a DevOps engineer solves “we need to do search queries” by standing up an ElasticSearch instance and writing code to ingest data from the DBMS into it. A DBA solves the problem by using the search-enabling features of the existing DBMS, and suggesting constraints on the way search is exposed at the business layer that make those queries easier on the DB.

Both approaches “work”, in the sense that you can do either and have a profitable company.