I would say it is much easier to write a convincing sounding folk tune than a song.
if we analyse both songs and tunes in the irish scots english welsh tradition,the melodies of both use four modes,major mixolydian dorian aeolian.
the tunes are often 32 bar double jigs slip jigs reels hornpipes.
writing convincing words that have the true feel of a traditional song[imo]is much more difficult.