'non-instructive' is formed from the negative prefix 'non-' (from Latin 'non', meaning 'not') combined with 'instructive' (from Latin 'instructivus', from 'instruere', meaning 'to build, arrange').

'instructivus' (Latin) changed into Old French 'instructif' and then into Middle English as 'instructive'; the modern English adjective 'instructive' acquired the negated form 'non-instructive' by prefixing 'non-' in later English usage.

Originally, 'instructive' meant 'providing instruction or practical teaching'; the addition of 'non-' simply negates that sense to mean 'not providing instruction', a straightforward semantic reversal rather than a major shift in meaning.