Done, no response, no timeline, no feedback, no one seems to care, bonus points for their being consistently unprofessional and lazy at each interaction.

Great point you raise, Montreal convention says after 21 days bag is lost. Turkish say it's not lost till we say it is and that could be who knows how long. Also travel insurance wont pay out until airline says its lost. Catch 22 right. It gets worse because Turkish have no office in NZ you can't take legal action against them. Bottom line, your ability to get a resolution with an offline carrier is remote, clearly Turkish don't follow the rules the ticket was issued under (Montreal convention). Secondly whilst Star Alliance is an alliance not all members operate to the standards you might expect. LH and NZ have previously lost baggage for my family, Located, returned and compensated fairly, professionally and promptly. Turkish....... well I'll let you draw your own conclusions!