"If the machine is so good, why did the major carriers who bought it spend zillions getting rid as fast as possible."
I have been with 3 MD-11 air carriers, I have held several positions, not a pilot but spent more than four years as a Maintenance Rep. or Flight Mechanic. Plenty of time to discuss with pilots and observe the aircraft charartistics.
To answer your question, the MD-11 was a reliability nightmare as it was cutting edge technology when first delivered. It had tons of "nuisance" pireps that did not have the support from MDC and especially Boeing to iron out all the issues in time. Boeing baught MDC to shut the MD-11 down to sell B-777's. Especially after the lack of tech support the guys on the line lost alot of support to resolve these issues.
EG: The fly by wire aircraft required constant monitoring of systems for given feedback (voltage and discrete) thresholds to log a failure. This was uncharted territory and as minimal faults generated by fault monotoring systems logged failures that were not actually significant but still out of design spec. It became a hard aircraft to maintain. Especially for PAX airlines who were operating many more aircraft that were not like it at all.
Fedex has been operating the aircraft for years and were able to apply the "nuts and bolts" approach to understand the aircraft better as they had been operating DC-10's for years as their "meat and potatoes" of heavy long haul aircraft.
I started out with an ACMI outfit that allowed me to work with DC-10's and MD-11's exclusively. This was great because the maintenance and flight crews could gain a better understanding of the aircraft. Flight crews became knowledgable of nuisance faults and maintenance could work better with them to resolve the issues for better reliability.
I currently maintain purely autopilot and navigation systems on the MD-11 and a few other airframes.
I do though miss eating breakfast at altitude watching a sunrise from the cockpit of this wonderfull machine. Those big windows give you the best view possible.