Titan was prioritized over a Pluto flyby for Voyager 1.
Voyager 1’s trajectory was designed to make a close pass by Saturn’s largest moon, Titan, after its Jupiter encounter. Titan was scientifically compelling because it has a thick, nitrogen-rich atmosphere and is one of the few moons known to possess a substantial atmosphere.
The trade-off was orbital geometry. A close Titan encounter would bend Voyager 1’s path so strongly that the probe could not continue toward Pluto. NASA therefore assigned Voyager 1 to Titan, while Voyager 2 followed a different trajectory that enabled later flybys of Uranus and Neptune.
This was not simply a choice between two equally available destinations. The Titan encounter had higher priority because its atmosphere could be studied in detail, and the spacecraft could not perform both the desired Titan and Pluto encounters. Pluto was eventually visited by NASA’s New Horizons spacecraft in 2015.