We've shifted to orbiters instead of one-shot flybys. Galileo at Jupiter, Cassini at Saturn, Messenger at Mercury, Juno on the way to Jupiter now. A ten year spacecraft mission can deliver a lot more science when it's orbiting a planet (or driving around on it) rather than cruising through endless void.
(New Horizons is set to flyby Pluto, because orbiting it wasn't feasible as the dwarf planet doesn't have nearly enough mass to capture a fast incoming spacecraft. New Horizons would have had to fly to Pluto much slower if it wanted to orbit it.)
(New Horizons is set to flyby Pluto, because orbiting it wasn't feasible as the dwarf planet doesn't have nearly enough mass to capture a fast incoming spacecraft. New Horizons would have had to fly to Pluto much slower if it wanted to orbit it.)