"Foe" is still very much a word, but it does sound a bit old-fashioned and poetic - even biblical - to modern ears. "The foes of democracy" is perfectly good English, and it makes for more striking rhetoric than "the enemies..."
I would say that "foe" is, in general, poetic or literary. But you do quite often see it in newspaper headlines because it's shorter than "enemy". You can find current examples of its use by clicking on the in context button within the WR English dictionary entry for foe.