The reason you see that is that you don't have view access to field storages.
In Drupal Core, there is no access control handler for them because they're managed behind the scenes and never really edited/viewed/deleted. That happens automatically through field configs.
You can add implement
hook_field_storage_config_access() (look for
hook_ENTITY_TYPE_access() for documentation) and allow view access to your users. But....
I'm trying to find a way to create an index for a content type based off of several of the fields found on each page.
I don't understand that. I'm not sure you're on the right track and before spending time to implement access control, I'd try to confirm that.