Sounds like the Dunning-Kruger effect hard at work. People get a good solid grasp of the basics and think they're experts because they don't know enough about the subject to realize that the basics aren't the whole domain.

Try exposing them to a few advanced topics in whatever they're overreaching on (like higher order functions for JS or named pipes in Unix). May not work, but you might get lucky and knock a few of them over the learning plateau and back on course to become real experts.