Hollywood appears to have an allergic reaction to Robin's presence in live-action Batman movies. The Christopher Nolan trilogy was dark and gritty — and therefore, Robin doesn't show up until a brief mention in the final moments of "The Dark Knight Rises." Moving into the Zack Snyder era, we only see Robin's Jokerized suit in the Batcave, implying he died before the events of the film. His death serves to make the movie even grittier and helps explain why Batman is a murderous near-villain during most of the events of "Batman v. Superman." None of the most recent live-action Batman movies really have a tone that sets the stage for a colorful kid sidekick.
The idea of Robin being "lighthearted," though, is turned on its head once Damian Wayne enters the picture.
Damian is more prone to decapitate a bad guy than shout, "Holy [insert anything]!" He was trained by assassins, and it's an integral part of his character that he has no qualms over murdering someone if it means keeping the city safe, often putting him at odds with his "no-kill" father. This makes for an interesting new dynamic between the crime-fighting duo and could help general audiences realize that this Robin must be taken seriously.
Remember when Aquaman was the butt of all jokes, until Jason Momoa turned him into everybody's favorite loose cannon? Momoa's take showed how you can take a character that the general audience sees as "silly" and turn them into a fan-favorite. "The Brave and the Bold" will probably continue the trajectory of dark, gritty Batman movies, but Damian Wayne can fit into that mold like other Robins won't.
