It is an approach to music (more than a genre) that relies on elaborate harmonic structures, freedom of interpretation of melody and personalising the harmony, interesting rhythms and time signatures and a general approach of trying to push the boundaries of music making. It is meant to be listened actively as opposed to having it as background music. The capitalisation of music has led us to the commoditisation of music and treating it as audio content as opposed to art.
> It is meant to be listened actively as opposed to having it as background music.
The masterpiece hanging in the museum was fully intended to be actively appreciated. The background on the box of cereal is ... just a background on a box of cereal. It's still art though.
That would be the distinction between "fine art" and "decorative art". Jazz as GP meant it is "fine art", the smooth jazz you hear in the elevator could be classified as decorative art.
I think that's a function of the effort, expertise, and intent. I don't think it changes the genre. Smooth, big band, blues, etc - it's all still jazz.
A low effort watercolor by an amateur is still (an attempt at) art and remains a watercolor even if no one appreciates it.
Most masterpieces where literally hanging in the background of some rich person's summer houses, and hunting lodges, and other properties. Thrown out and replaced on a whim.
Art was used by the rich and famous to show off their wealth.
In the 19th century countries got into the game (the idea that Dutch masters were ending up in American collections was a national embarrassment).
The term covers a variety of styles, with old ones hanging around as new ground is broken. Perhaps it is a "meta-genre". There are various articles around explaining its history which might be worth looking at, if you're interested.
I'd expect to hear some degree of improvisation in jazz, but not in easy listening.
The original quote is apocryphal, but he did respond to a question from a reporter asking about the quote saying, "Yeah, Daddy. Ya know how it is... jazz is something ya feel... ya live it, that's all." So he wasn't gatekeeping, he was saying the answer to "what is jazz?" was contained in the experience of jazz.