Inconsistent characters: Ivy is a misanthrope who can't stand being around people. She is perfectly fine being in common areas in prison and goes to a party and hangs out with another person. When some people are being turned into plants, she turns them back into humans. Harley and Ivy don't give a shit about a kid and his parents being eaten by Ivy's pet plant but these kids matter, kids whose friend was going to kill Harley.
No rules: the Joker and Harley can go around mass-murdering, but no superhero is out to stop them. "Secret" lairs are built all around the city but superheroes aren't able to find them. Unless there's some big reveal about how law enforcement and superheroes are in it together with the supervillains, it just feels like nobody gives a crap that people are being mass-murdered left and right.
The one joke: the show being a comedy, this is the worst offense. They're doing a heist but they bicker about delivering their lines. The Joker doesn't care about killing people but he has to build to code. They're doing a mundane conversation about takeout food, they're just like regular people. The super-agile spinny ninja girl who can take out an entire complex full of armed Joker goons hurt herself doing a flip in a chair. Supervillains gossip at the office kitchen. Look at all these jokes about how mundane things contrast with the crazy world of supervillains! Let's do this joke five times an episode.
The other jokes: Harley was going to rob the Gotham Mint but it was just one room with an improve troupe pretending to be guarding a safe. What? Why? She can't tell the difference between a real mint and a back room at a party? Maybe if they established that she was drunk/high first this would have worked. Harley angrily doing <contemporary dance>. Joker murders a celebrity and this slightly disappoints a murderous plant and Ivy, a misanthrope who wants to exterminate humanity, because the murdered celebrity is such a nice person.