“Lucky”, only in the sense that (1) completing a large government project on time, and (2) not having some kind of disaster (particularly, at launch) screw up the mission require a certain degree of luck of luck on top of planning and execution (though, not relying completely on that luck is also why there were two Voyagers): we got all the gravity boosts because the mission was planned around an alignment that enabled it to do that and visiting each of the outer planets (which was really the main goal; the beyond the solar system part was gravy.)
The New Horizons probe was launched at much faster speed than Voyagers, actually beating the record of the absolute fastest launch in history, but because of not getting those gravity assists it will never overtake Voyagers.