It is impossible to become good at "public speaking".
That's because "public speaking" isn't just one skill. We have unfortunately bundled many different skills under the one phrase. Confidence, energy, clarity of ideas, and maintaining a connection with the audience are all crucial for a great performance, but it is impossible to simultaneously improve at so many disparate skills.
Maybe it's easier to explain with an example. I'm assuming if you're reading this blog, you're probably a software engineer.
"Learning to code" is not a single skill. It's a collection of hundreds of ideas, and they are learned a bit at a time. We first teach how to print "Hello World!" before explaining variables and functions. We teach functions before building operating systems.
You can take the same approach to public speaking. Identify an small area to improve, and keep practising until you're good at it. Perhaps you're looking to improve your confidence on stage. Maybe you want to work on delivering a message that sticks. Or, maybe you need to convincingly pitch your project idea to management.
You can be a better public speaker. Be extremely specific about your goals, ask for help, and relentlessly practice until you improve.
You can do it.