Having a DBA certainly would've helped them when they accidentally deleted their prod database with no backups too, that probably wouldn't have happened if they had someone who knew how to properly manage DBs
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.
Choosing the right data types for columns is not "solved" by switching to entirely different RDBMS's. Particularly for the TEXT requiring a length comment. None of these reasons were discussed or deliberated in detail as people point out in the comments.
Given the prevalance of that attitude, I'm a little surprised to see that the general tone of responses here is "This wouldn't have been a problem if they'd just hired people who knew what they were doing." The point is, they didn't. They hired devops engineers who knew enough to solve common problems, in line with the conventional wisdom here. Their stated reasons for ending MySQL support are perfectly in line with the view that specialists are a waste of money. Indeed, I'm not sure what other outcome should have been expected.