Apart from Ms Carey's seriously ill-advised wardrobe selection - she has neither the height or the shape to carry off a clinging outfit like that - she is faced with the issue that the more technical stuff involved, the more potential for disasters.
I have no problem with bands creating material which it is not possible to reproduce on stage - the cessation of touring freed The Beatles to enter an entire new universe of music production without the constraints of wondering how to take it on tour with them.
But in that case, a band should be able to create a version of the song that works well when the band play it together (as bands should) - an excellent example of this is Fleetwood Mac.
But the advent of seriously over-produced and technically constructed pop, of which Ms. Carey is a queen - means that reproduction is fraught with such difficulties, and she had to stand there while a pre-record ensured that the audience heard all the top notes of her famous five-octave range, even if she was not going to attempt to create them herself.