Despite the relative age of the type, OS 767 fleet is actually not older than significant parts of the rest of OS fleet.

Crucially for this discussion, three of the 777s are older than any of the 767s (including the parked one), two others are barely younger. Only one 777 is significantly younger.

Situation is not much better at the narrowbody end, a number of A320s are legal to drink in USA, and only one A321 can claim not to remember Y2K (but it would 9/11)