The one called ‘Default’ is actually a custom authorization server, so no, you cannot use it without the API Access Management feature or in an org that otherwise is allowed to use it.
Without this feature, the only authorization server you can use is the Org one, which does not support the ability to create custom claims, scopes, or access policies and will not work in certain use cases. More details here:
https://developer.okta.com/docs/concepts/auth-servers/#available-authorization-server-types
Difference between Okta as an Authorization Server vs Custom Authorization Server | Okta Help Center