A large amount of Voyager 1 & 2 's success isn't just technological it is the ability to take advantage of a specific planetary alignment for a gravity assist [1] that can only occur every 175 years [2] .
[1] https://en.wikipedia.org/wiki/Gravity_assist [2] https://en.wikipedia.org/wiki/Voyager_1#/media/File:Voyager_...
Fingers crossed, if we manage not to blow each other up until then, we have 126 years to go till we can try again.
Every 20 years, Jupiter and Saturn are in position for a gravity assist, which allows you to reach half the outer solar system. In the 1970s, Uranus, Neptune and Pluto were all in the right half.