Bert, I agree with you. It's not only PBS, but the broadcasters of children's TV in the UK, too, who need to "hire someone who can talk", as you say.
I know I'm going to sound like "Disgusted of Tonbridge Wells", but I am appalled by the slovenly, poor speech of the children's TV presenters - especially the people who act as a link between programmes. Here is a possibility for good role models that has been totally thrown out of the window.
Everything is also so frantic, and there is little opportunity for children to quietly and simply listen and absorb. I think there was an attempt in the past year or so to revive the story-telling slot "Jackanory" - but I'm not sure that it came back for long.
I do drama work particularly with children aged under 11, and it seems to me that their capacity for calm, quiet, attentive listening and absorbing (and accompanying use of their imagination) is decreasing year by year. No doubt there are other factors to explain this, but I'm sure that the current general style of children's TV (there are some good exceptions) has a lot to answer for.