Suicide Squad: 8 Reasons Jared Leto's Joker Is The Worst Part Of The Film
6. The Plot Reduces Him To A Love Interest
Ultimately, even if there was a really good idea powering this version of the Joker, it's all rendered moot because in the movie as-is he's never elevated to anything more than a love interest.
Even though Dr. Quinzel's fall from sanity is presented as a one-way trap, it seems like Mr J was likewise smitten and became a doting partner; every scene he appears in is all about him reuniting with his love, the film giving no time to define him independently. This is of course always a risk when he's seen almost entirely from Harley's perspective, but there's literally nothing else given to really expand his role.
What makes this especially frustrating is that in an earlier version of the film would have likely made this a real strength; their relationship was going to be a lot more volatile, with proper mental and physical abuse and some dissection of how this disfunction works (or rather, doesn't). In the movie we got, Joker's nothing more than a clingy boyfriend stalking his partner on a night out.