Persuasion requires that you look individuals in the eyes.
Judgement. When most people are giving a speech they willfully ignore or are ignorant of the response written on the faces of every single person within earshot.
It is much easier to look out on the crowd, parsing the audience not as individuals but as clusters of people that you are vaguely pointing your message towards. This is a mistake. To truly communicate, you must look directly at an individual within the crowd. Look them directly in the eyes, for just a phrase or two and speak directly to them.
They will look directly back at you, your eyes locking, and, in that moment, you will be able to read the judgement of your message directly on their face.
Their judgement will give you exactly what you need to know; am I saying something that captures their interest? Am I saying something they understand? Have I crossed some personal or cultural line? Do they want to know more?
Each person, whether they want to or not, will have their evaluation of you in real time and if you can force yourself to look at the scary dragon of another person’s judgement you can adjust, not necessarily to make them like you or what you have to say, but adjust to make certain that you are making your message understood.
The crowd can give you feedback, but the judgement written on the face of the individual will tell you everything.