New Delhi, Oct. 23 -- I noticed a telling detail in the first episode of the ninth-and, we're promised over and over-final season of Koffee With Karan (streaming now on JioHotstar). During a patently unremarkable conversation with Salman Khan, the show's multihyphenate host Karan Johar revealed that he does not, in fact, drink black coffee and that his cup happens to actually contain Diet Coke. As easily dissolvable metaphors go, that is a fine one for what the once-iconic series has become: a synthetic (and overhyped) cola in place of a natural drink that sharpens the senses.

When Koffee With Karan began back in 2004, it offered something genuinely zingy. An insider seat within an increasingly insider industry. Here was star filmmaker J...