Thanks, that's a lot to think about. I had always seen Eisner's art described as cinematic (the pacing, close-ups, use of shadow), but now that you mention the theatre, I see where that predominates.. particularly in his later work. There's quite a bit of the lone figure in a spotlight on a darkened stage.
And it's true that comics have traditionally been aimed at juvenile audiences with the problems of adolescence and young adulthood explored. Eisner was increasingly concerned with aging, loss, sorrow. so it's natural his post-SPIRIT work would have that tone. It can't really be expected to be exhilirating.