Public speaking is not a team sport. That's why most good speakers have had a speaking coach. A speaking coach works with you, the individual. You have a unique voice (you don't have to tell your mum who you are when you call her - she knows your voice intimately.)
You have a unique story and you have lots of stories that you can weave into your talks and presentations.
You have a unique style and your own brand of humour - you don't need to copy anyone. You are enough. You are unique.
You probably don't have all the contemporary speaking techniques. "Do it Yourself" doesn't really work for learning to speak confidently.
And you can't give yourself feedback. You can't do your own critique. It takes that "look from the outside" which is why good speakers have a good coach.
I sing, so I have a Voice Coach. I play Squash, so I have a Squash Coach.