It's interesting to compare the learning of programming with the learning of elementary algebra. Both involve abstraction, which I think requires brain re-wiring. And that takes time.
FWIW, programming (coding) is in the process of being introduced into the primary school curriculum in New Zealand, so your concerns about students having to pick up computing from scratch should ease over time. I just hope don't we find ourselves in the same situation as Maths, with many students becoming programming-phobic.
Certainly I think code profile tools like the Python visualizer are attractive. I just don't know how to get students to appreciate their benefits. It seems to me (hypothesis) that the students who don't actually know what their program is doing are the ones least likely to explore the use of extra tools to help them improve their understanding.
Richard