These two concerns are not mutually exclusive, the kind of database or data stored within it doesn't give any availability guarantees on its own. Even a single Postgres instance, which I suppose fits your understanding of a real database, is a single point of failure and not a highly available setup: If your database server goes down, clients get errors and the database is thus unavailable.
Just because it works for your use case right now doesn’t mean there isn’t room for improvements to support others too.