In my experience, AI raises the ceiling but also lowers the floor. It can make experienced people more productive: they can vet the output. The juniors? Not so much. I've worked with guys who write prompts that are literally "fix it." The result is about as good as you expect.
"Productive junior" is vastly different than a productive software developer with a couple decades of experience. What they produce will differ in quality significantly, AI or no AI.