I think the 340 was the right aircraft at the wrong time. It was sensible to plan a long range machine but the speed with which ETOPS progressed could not have been know at the time the project was agreed. I recall the captain of a -600 telling me how fabulous the wings were, "The big change when moving to the 340, is that it takes longer to slow down than others, because the wing is so good."
In my telecomms career I saw something similar with a particular large PABX as used in the late 80s and into the 90s. By the distinguished company with a great track record had it ready - its technology was out of date and they never recouped their investment. Not unlike the 380.