The only memes I see are from meme communities, and I see a bunch of communities dedicated to thoughtful discussion, because I'm subscribed to them. I never look at the frontpage, I only look at my subscribed communities, and I'm only subbed to a minimal amount of meme communities. If I unsubbed from them, I wouldn't see memes at all.

Also, the world is fucking dark and shitty. Sometimes people would rather make jokes about it than talk deeply about it because they're trying to not go crazy and end up suicidal from facing too much darkness. Humor is often used as a release valve for painful subjects. Why not let the people who don't have it in them to get into lengthy discussions just handle it in whatever way works for them.