So are you suggesting this A/C can only be maintained by people with some sort of "specialized knowledge" or specific "factory training".....?
Lets put it this way, it ain't a Boeing, nor a Douglas...and you had better understand the systems (and have the specialized tooling) to maintain the airplane properly.
The largest operator of the type was Delta, with over sixty...and a senior VP told me personally that the 'ole TriStar made more money for Delta than any other type, operated at the time.
Now, if the airplane was so successful at Delta, one wonders why other airlines had such a difficult time?
TWA did well, so did Eastern, as did ANA.
RJ had no complaints, and indeed the airplane held up rather well at SV, and at CX, where it made handsome profits for that far eastern carrier.
Even little UL, who operated seven for quite a long time, maintained out of a blister hangar at Colombo, did well.
I would then ask again, why were some carriers (especially BA) so apparently unsuccessful with the type?