Considering that their most important function is to entertain us, many of those memes out there aren't especially cheerful. Much like art is supposed to be a reflection of the world, memes take a long hard look at the state of things and try to give an honest reflection of what they see, whatever that may be.
It's not always predictable what is going to come out the other end. Sometimes it gives a light-hearted look, and others, it's pretty dark. Occasionally, the resulting meme is something which doesn't even make much sense. However, one thing we can guarantee is that it will follow ever-shifting but successful rules of internet humor.
There isn't always a magic formula, and not everything gets it right. Luckily, there's plenty more where it came from, making it easy to pass up the duds and move on to the next one. We never see the end of the conveyor belt of memes.