Not so much new-fangled, perhaps, as "classically" influenced.  Carolan was certainly influenced by the fashionable Italian composers of the day.  I suspect that whoever told you that he was too modern to be "traditional" was having you on, or possibly didn't really know what they were talking about; he worked within a traditional idiom but incorporated outside influences where it seemed appropriate to his market.  He had a living to make, after all.   If Carolan is too recent to be considered to belong to the tradition, then so is almost all of the instrumental music being played in Ireland at present!

Malcolm