Regarding the issue of ageing composites, it seems that the composites within the tail of N14053 aged graciously because:
NASA's and Airbus' FEA models determined that failure of the rear main attachment lug was the most probable initial failure. The FEA models and NASA's PFA model also determined that the failure initiated at the final observed maximum vertical stabilizer root bending condition during the accident flight, when the vertical stabilizer was subjected to a global root bending moment of more than two times the value defined by the limit load design envelope. (As previously stated, for certification, the vertical stabilizer is only required to support loads of 1.5 times load limit without catastrophic failure.)
as stated on pages 68 and 69 of NTSB report. Couple of previous pages contain methods applied in analysys of fin and rudder. More of it is in other documents available within public docket. If you're still convinced that there was unprovoked delamination or that fin failure started from the front, please read the report and tell us exactly with which part you disagreee and why.
What difference would made if fin was metal instead of composite? Do you think that it would be beefed up to stand 3 times the load limit? Me not. This fin exceeded regulatory requirements by very healthy margin. Perhaps metal would bend before breaking, but that would be hardly helpful.
Accident investigation is not about approportioning the blame. Goal of accident investigation is to gain understanding of particular accident, so its reoccurence can be prevented. By listing F/O's rudder input as primary contributory cause, NTSB didn't say he was to blame or should get punished, just that he did so-and-so and consequences were such-and-such. Blame and punishment are best left for religious and judicial entities.