I know you don't understand it. Conservatives have a hard time understanding the concept.
Memes are a language. They communicate several layers at once.
So, imagine if you will, that you have only heard, seen, or been exposed to one language. Not even the idea of someone speaking a language other than your own has even come up.
Then, one day, you discover that there are people who speak but you can't understand them. The sounds are similar. The symbols are similar. But they have no meaning for you. It appears to just be babble. And because it's a language you don't understand, you immediately dismiss it.
"Those people over there? They can't speak."
So, when conservatives say "the left can't meme" what they really mean is "I don't understand, and I'm not going to try to understand."