It can be done though. It depends on the sample library and the user.
This goes with what I was saying in that other thread about the BBC Orchestra and being burnt out: A great deal of orchestral sample libraries do not offer enough articulations and samples beyond "long" and "short". This is not necessarily because of an inherent inferiority of samples unto themselves, but because most of these companies are throwing all the budget at recording big-name orchestras, in big name halls, with big-name engineers, and run out of $ before they get around to sampling much beyond basics.
Plenty of recent soloist libraries and a handful of ensemble ones do go further though, and used in tandem, they can play a fairly extensive repertoire and still sound convincing. Provided that the MIDI orchestrator knows what he/she's doing, of course.
Really, the objective difference between a live musician and sampled musician is that the former provides you with an unlimited amount of different "samples" (provided you have limitless cash) and often greater homogeneity of the performance (most of the time), but unlimited cash cannot buy you unlimited samples in software format — if you don't have a sample of it, you can't truly "mock it up". Live players can give you any "sample" you want.
So while Elfman is definitely correct that live players are ideal and offer a number of advantages — be they in performance, time efficiency, "human-touch", etc. — it doesn't mean that writing the kinds of music he writes is too difficult to justify using samples to create, nor does it mean he isn't out of touch with the rabble.
But any of us among the peasantry expecting to find understanding among wealthy, Hollywood celebrities who make a living at something less than 1% of the population does or even can do, is looking in the wrong places to begin with.