Corbyns problem has never been his domestic economic agenda, its him personally, his defence/overseas agenda, and his baggage. the polling supports that - when people are asked about anonymised policies they, from all over the political spectrum, give high approval ratings to the policies you've outlined above. however, as soon as you put Corbyns name next to them you may as well have suggested drowning puppies while getting your knob out in a junior school, the approval ratings for those polices nosedive.
its him, the electorate - and i take this from polling and my own doorknocking experience - don't like him. they don't trust him or like what he stands for and who his friends are in the defence/security/overseas sphere, and they don't think he could run a whelk stall, let alone a government, in the domestic sphere.