Here's the fixed code for whoever needs to retrieve the Subscriber Status from All Subscribers with AMPscript:

    %%[
    
      VAR @rr, @sfp, @requestStatus, @requestId, @allSubRows, @allSubRow, @subStatus
    
      /* Creating the RetrieveRequest object with the SubscriberKey and Status as properties */
      SET @rr = CreateObject('RetrieveRequest')
      SetObjectProperty(@rr,'ObjectType','Subscriber')
      AddObjectArrayItem(@rr, 'Properties', 'SubscriberKey')
      AddObjectArrayItem(@rr, 'Properties', 'Status')
    
      /* Creating a simple filter based on SubscriberKey for the RetrieveRequest object */
      SET @sfp = CreateObject('SimpleFilterPart')
      SetObjectProperty(@sfp,'Property','SubscriberKey')
      SetObjectProperty(@sfp,'SimpleOperator','equals')
      AddObjectArrayItem(@sfp,'Value', @subscriberKey)
      SetObjectProperty(@rr,'Filter', @sfp)
    
      /* Invoking the Retrieve Call */
      SET @allSubRows = InvokeRetrieve(@rr, @requestStatus, @requestId)
    
      Output(Concat('requestStatus: ', @requestStatus))
      Output(Concat('<br>requestId: ', @requestId))
    
      /* Looping through all found Subscribers - Ideally would be only one */
      FOR @i = 1 TO RowCount(@allSubRows) DO
    
        SET @allSubRow = Row(@allSubRows, @i)
        SET @subStatus = Field(@allSubRow, 'Status')
    
        Output(Concat('<br>subStatus: ', @subStatus))
    
      NEXT @i
    
    ]%%

Just remember to set beforehand the SubscriberKey in the @subscriberKey variable and it'll work just fine!

For example: `SET @subscriberKey = AttributeValue(_subscriberKey)`