This cannot be said enough🛐💖💕
Yes, Chu Wanning had a crush on a teenager, his student. No, he didn't do anything abt it. That's the point. THAT'S THE POINT.
Chu Wanning is convinced that he's completely undesirable, yes, but even if he thought he had a chance with Mo Ran back in the early days he wouldn't take it, because Chu Wanning is an extremely morally strong man. In canon, he would not begin an affair with an underage student who is dependent on him, his desires do not outweigh his morals.
And having desires isn't bad. Even desires that contradict your morals aren't the end of the world. It's how you act that matters.
This isn't worded as elegantly as I'd like, but this is one of the points that really makes me love Chu Wanning. He desires things that make him hate himself, in a lot of cases completely unnecessarily. I love reading the story and watching him reconcile with the parts of himself that he's written off as disgusting, watching him come to understand that he's loved and loveable just as he is. He's rude and mean and a pervert, and he's loved.