Great question!
All points being made here are good; Now my view.
Big Band still has a good size audience but it depends how they are played. This includes all keyboard settings and your ability to get excited.

I feel that Big Band music must be played with a stronger flavor; Stronger basses and drums and more exciting soloing. Just listening to some of the old recordings they will tell you they are out.
Years ago I thought the old rhythms were great but no longer. The beats/styles I select are exciting, if not I do a bit of editing. If you are moving them in and from their seats, and the song is familiar, Ya got em!

It is not always what but how we present whjat we play that makes us successful. Big Band is not a substitute for 50’s, 60’s and 70’s -- But they can add to your job. If the average age is between age 23 to 43 I try not to show up on the job. (smile)
John C.