I understand what the author intended, but the formation of that sentence is poor. If I state that Blues has had a wide influence in modern music, leading to Jazz, Rhythm and Blues, Rock and Roll and Duran Duran … this statement is not incorrect, but don’t you think “Duran Duran” is a little out of place?
Duran Duran does not represent a major branch of modern music. English is not a major language family. But I believe Greek, Latin, and Celtic are considered major language families. It's just awkward to make English a fourth "example".
I don't think Greek is a major language family either, but it is interesting to note the importance of the latter three of the four. At some point in history, each of those three languages has served as a lingua franca to a greater or lesser degree. Before the Roman Empire, anyone with a working knowledge of Greek could do business in any of a hundred port towns or trading communities from Tarshish to Tashkent.
Later, Latin served the same function over an even broader geographical range, being used by the Church long after the Roman Empire had been replaced by the Holy Roman Empire.
Today, English is the language of world communications and commerce. Though the World Wide Web spans the globe, well over 90 percent of its content is in English.
I don't know if Celtic ever served as a trade language across cultural boundaries, although it might make for some interesting study. It may be too remote in time to draw any meaningful conclusions.