Yeah I don't disagree with what you're saying, we don't put fresh grads on jobs without adequate supervision on the design side either. On both sides of the "fence" you need the experience to produce a good product; the two jobs are different and should be complimentary.

The schemes I have worked on that have been the most successful have had the designer and contractor working together closely from an early stage to produce something that works well, drawing on the past experience of both to anticipate potential issues and design them out.

Personally it took me about 6 years before I felt I was good at design. Experience really does count.