Your success will depend entirely on your ability to communicate well. I don’t think that’s an overstatement. If you can write well and speak clearly — able to effectively communicate the thoughts in your head so the other person understands exactly what you are trying to say — you are on your way to effective leadership, compelling thoughts, and convincing people to see your perspective. Conversely, if you can’t communicate well, your success will be limited. As a first step, invest the time in learning to write effectively, even 2-3 sentence-long emails. If you write effectively, your speech will also become more coherent and compelling.
A bonus of learning to communicate effectively is you also learn to THINK better. If you can’t explain it well enough, you don’t understand it well enough. So learning to communicate it also helps you learn to think through it.