One of the main recognizable factors of how horrible the characterization of Fanon Dick is that the individual who's a cereal obsessed Himbo with zero brains and always sunshine and rainbows is someone who could NEVER pull off the persona of Batman.
Fanon Dick is the same as a literal doormat. People often forget that Dick can be scary and serious if he needs to be. But he isn't because he knows it won't always help the situation at hand. He can EASILY command an air of authority, respect and obedience in seconds if he wants to do so. Which is why he played the role of Titan Leader and Batman so well.
But he doesn't. He acts less stiffer (i won't say soft) than Bruce and provides gentleness to those who deserve it. There are a million reasons why he doesn't want to be Batman but i'm sure that one of them is definitely that he doesn't want to stay in that constant state of a Commander.
Yes he's lighthearted but that doesn't mean he can't be as scary and serious as Bruce can be.
If any writer ever wants to know how to write them, ask yourself if you can imagine your characterization of Dick in a position of leadership and control, as well as compassion, lightheartedness and flexibility (pun intended) if needed. If both criteria's don't meet, that is not Dick Grayson in my opinion.