How important is speech writing? Very. So is the editing of that writing. What about rehearsing? That too. Remember, what and how you say things is what distinguishes your presentation from a silent, humanless slideshow. You are the distinction. Your presentation should work without the slide deck. The slides are there to augment and amplify what you say.
Often, speakers get lazy with the writing. “I know this stuff. I’ll just speak from the heart.” This can lead to shapeless rambling. Do this and you’ll miss an opportunity to control your presentation strategically.
Editing is hard. “It’s good enough,” is a phrase wannabes use. Leaders take editing seriously.
Maybe they depend on their slides to walk them through their presentation. Similarly, they wing the delivery, reading from their slide notes. If that’s the case, any warm body will do fine. They don’t need you.
A great speech is like a song: every word matters. So, hone those words. And hone your delivery.
There is no hierarchy between writing, rehearsal, and slide deck building. If you want excellence, be excellent in each aspect. Anything less is average.