Absolutely, but the context "afterthought" narrows the situation to a very specific case, that in which you have given no consideration at all about accessibili

Absolutely, but the context "afterthought" narrows the situation to a very specific case, that in which you have given no consideration at all about accessibility. My belief is that if you were able to produce good markup, it would have been accessible from the very beginning, because accessible markup tends to be well-formed and semantically correct. This would probably rule knowledge of WAI-ARIA out from everyone who fit parent's case.