You still need it. There are tools included with Postgres that you can cobble together for a backup solution that is lacking in features and edge case testing. But i'd much rather just use the right tool for the job.

For example, pgBackRest solves real problems with features like block level incremental backups that drastically reduce storage and transfer times for many workloads, automated backup retention policies, multiple repository support for offsite backup redundancy, encryption support, point in time recovery for granular restoration capabilities, and tooling to build standby servers very quickly and efficiently. These features handle edge cases and reduce operational overhead compared to managing scripts around pg_basebackup and WAL archiving yourself. In many environments, those features are required (e.g. encryption).