If you have a low-volume, non-performant, non-critical database, k8s is fine. If you need it to perform and/or need built-in ops (managed backups or replication), use a managed service.

k8s _can_ do stateful, but if a managed service exists for this workload, use it. It is not about _can_ I run it on k8s, it is a _should_ question. Is it worth the cumulative effort required to achieve the same degree of quality.