I outline novels. I don't outline (most) short stories.
My outlines emerge out of pages and pages of notes where I brainstorm story ideas and character ideas and situations and anything else that comes to mind. The whole process usually takes 1-2 weeks. The final result doesn't look anything like what an English teacher would call an outline. It's more a series of chapter summaries, describing what happens.
I never completed a novel project I didn't fully outline. I think it's because Middles are my Kryptonite.
I've never written a novel to The End without also adapting/evolving the outline as I went along. No battle plan ever survives contact with the enemy.
I figure everyone will eventually find their own way to write. Or not. ;-)