James Gunn left the Joker out of The Suicide Squad because he'd be useless in a fight
James Gunn actually had a good reason not to bring back Jared Leto's Joker, and it's not because he sucks
Nobody should ever need to actually come up with a good reason to leave Jared Leto’s Joker out of a movie, since he’s Jared Leto’s Joker, so kudos to James Gunn for actually having a solid answer—beyond “because he sucks”—for why he never considered having Leto stencil “damaged” (or maybe “the damaged” in honor of the sequel’s title) on his forehead and pose with a bunch of carefully arranged knives in his The Suicide Squad. Speaking with The New York Times, Gunn explained that he never considered bringing back Leto’s Joker from the David Ayer Suicide Squad movie because “he wouldn’t be helpful in that type of war situation.”
Gunn’s The Suicide Squad, as seen in the trailers, largely seems to take place in one big warzone, which is why he has assembled a much bigger cast of no-name DC villains than the last movie, and it really makes perfect sense that there’d be no reason to bring the Joker along for a mission that seems to require some level of strategy and… you know, competence. (One could also argue that Gunn’s reasoning is a subtweet in the direction of Zack Snyder’s Justice League, which added a scene where Joker was on Batman’s team in the post-apocalyptic alternate future or whatever, but we’re going to assume that Gunn had better things to do in 2020 than watch that movie.)
The New York Times also asked Gunn about Will Smith, who backed out of The Suicide Squad before even being officially attached due to some kind of scheduling conflict, but it sounds like the director never really intended on using him in the first place. Idris Elba’s Bloodsport is replacing Smith’s Deadshot as the “very competent gun guy” archetype in the new movie, and Gunn says he just “really wanted to work with Idris” in something and figured that Elba would be good at pulling off the “gruff, Unforgiven-type feeling” that he was looking for to center his movie around.
Elsewhere in the interview, Gunn talks about how he found out he had been fired from making a third Guardians Of The Galaxy movie (before later getting rehired) and offers a nuanced reaction to “cancel culture.” He also mentions that Warner Bros. approached him almost immediately after all of that happened and asked him to make a Superman movie, but he chose to sit back and find a project that he really thought could be “great,” and that’s how he landed on The Suicide Squad. It’ll be on HBO Max and in theaters on August 6.