You've got the technical definition correct, but the vast majority of usage of the term meme today is the colloquial usage, which is centered on humor, and has only a passing similarity to Dawkins' idea. Really, it's used today as a replacement term for what used to be called an "image macro", but also extends to cover video content.
For better or worse, that ship has sailed. Convincing people otherwise is going to go about as well as convincing them to not use "literally" in a figurative sense.
Basically, it's the smallest unit of cultural information. In the same sense as Gene it's the smallest unit of genetic information.
That's why it's pronounced Meme as in Gene.
None of this necessarily implies a joke.