WHBM
The MD-11 wasn't really a modern design. McDDouglas tried to do a quick and cheap derivative of the DC-10. It ended up being neither quick (many delays) nor cheap.
By the time it entered service the 777 and A340 were well under way and were much more efficient: lower weight and operating cost.
Most potential (and existing) customers had lost confidence in McDD by then. Any handling difficulties were just an extra nail....