We added a feature flag because [GitLab-#11582](https://gitlab.com/gitlab-org/gitlab/-/issues/11582) changed how public groups use the Dependency Proxy. Prior to this change, you could use the Dependency Proxy without authentication. The change requires authentication to use the Dependency Proxy.
In milestone 15.0, we will remove the feature flag entirely. Moving forward, you must authenticate when using the Dependency Proxy.