"Is it that the audiences aren't what they used to be - or the buzz no longer lifts the hairs on your neck?"

Both.

Mind you if I could find the right combination of musicians to perform with acoustically (but amplified), the audience's reaction would be quite incidental in terms of the fun it would be to "cook" with these "boys"/"girls".

Unfortunately most of the people I'd really like to play, perform and could be coerced to getting on stage with, are either dead or live far far away. C'est la vie.