I could maybe understand in the old days, but these days we have fax and email.
Literal
Long-ago [if-なら] well not-know, now [topic-は] FAX [also-も], email [also-も] exist.
~ならいざ知らず is a fixed expression meaning 'if it were X, that would be one thing (I wouldn't know about), but...' — used to dismiss an excuse as anachronistic or out-of-touch. いざ is an archaic interjection ('well then, come now'). The pattern introduces a counterfactual 'if it were like that' and then pivots to the present reality. A good example of how Japanese preserves classical vocabulary inside fossilized constructions.