How is Doomfist usable?

For the love of god I do not understand how in the hell Doomfist is at all usable in any situation. It seems I need to commit 90% of my offensive options to secure a single kill, maybe, which means I will be a sitting duck immediately after. On top of that the Rocket Punch has been near unusable for forever and a day. Can someone please explain how this is supposed to work.