On filling in detail:
In the movie 42, Branch Rickey is trying to get Jackie Robinson to the Major League Brooklyn Dodgers. His field manager, Leo Durocher, is skeptical, even hostile, but stands by his boss when it hurts. Then Durocher is suspended for a year over a scandal, and Rickey has to find a new manager. He taps a retired manager (whose name I forget). That manager says "I promised my wife I would never put another uniform on." Rickey counters "You don't have to wear a uniform. Manage in a suit like Connie Mack did."
Leaving aside why Connie Mack wore a suit in the dugout, this fellow's argument with his wife would have been red meat to any screenwriter. But we never see it. Why? Because it's not part of the story.
Leo Durocher did not manage during Jackie Robinson's rookie season, and that's a detail that deserves to be filled. But it was filled quickly, in four short scenes: Durocher misbehaving, Commissioner Happy Chandler delivering the bad news, a very abbreviated scene with Rickey and Durocher, and the discussion with Durocher's replacement. I doubt it was five minutes of screen time.
Jube, you and I err on opposite sides of the side story. I am stingy with description in order to keep the focus clear. (I fail in that goal in other ways.) You include so much detail that description grows runners and sets down side-story roots.
I'm thinking now of two of John Dickson Carr's Henri Bencolin novels and their perorations. In The Corpse in the Waxworks the climax occurs by a telephone call. In The Four False Weapons (IIRC) there is a scene in a private casino. Both are full of tension; both come alive. I have to go back and see how the description is handled. The Sleeping Sphinx is another of Carr's stories to revisit. It feels description-heavy. Whether it is or not is another matter. (It is also, IMO, one of the best detective novels ever written. Opinions differ on the matter.)