The tapes from the show indicate that the audience reaction was relatively strong ... but you can hear people in the background wondering where his "greatest hits" were.
The reviews for the show were mixed to say the least, and I think that's the raason Elvis went back into his comfort zone the following night rather than how the audience reacted.
I think he should've ignored the audience and press, and continued with shows like this. Got rid of the 2001 theme and the jumpsuits forever, and mixed it up a little.
Elvis doing the same show night after night after night for almost five years (1972 to '77) played a huge part in his bordeom, IMO. He had enough material to deliver several types of shows, and he could've mixed it up more.
But he made the choice not to, for whatever reasons.