The focus of Kaddish has to be sanctifying G-d’s name in THIS WORLD. This form of sanctification requires 10 men. Most other forms of sanctification do not require the presence of 10 men. Other forms include keeping Mitzvos one is obligated to do, doing acts of kindness and any behavior that enhances the image of those who keep Torah and Mitzvos.
When children sanctify G-d in this world, the parents’ souls gain benefit.
Kaddish is not a prayer for the dead, nor a tool of manipulation of other world.
“He was bragging about his behavior in shul last Friday night.”
Either he is completely ignorant about the meaning of Kaddish or an apostate.