Sure, knowing your database well enough to "manage it" in terms of indexes, bloat, writing procedures, that's a developer responsibility.

What is "new", is developers having to manage the DB backups, k8s clusters, Docker images, Terraform, load balancers, CI/CD, proxies etc.

This used to be a role for a whole another role. Some places do have an "Ops" role, but most tasks are still expected off the developer, with Ops at best providing a helping hand, rather than taking over a task completely.