There has been great speculation that Nick desired to have a homosexual relationship with Gatsby. This meme seems to play off of that joke, with Nick being unhappy that Gatsby would rather have no relationship than one with someone other than Daisy. I personally never saw this when reading the novel myself, but I can see how others find this theory to be true. Nick has almost no female love interests. He has something with Jordan Baker, but that goes nowhere. I always thought that it was because she was a modern woman and mildly problematic, and Nick did not want to be involved in her side of the drama she caused. However, just because a male character does not have any female love interests, that does not automatically make them interested in men. When reading the novel, I did pick up on an unusual obsession that Nick had for Gatsby, but I never associated it with anything sexual.
For a relatable perspective: almost everyone has fallen in love, and when it ended, you could never imagine yourself or the other person in a relationship with anyone else. That is one of the worst feelings in the world, especially when you see them with a new person and you have no one. Daisy and Gatsby were in love, about to run away with each other, then life got in the way. They had to split paths, and she ended up with a new guy and Gatsby was all alone. He can’t imagine being in love with anyone but Daisy and has no intention in doing so anytime soon.