On its own, it's a pretty solid movie. There were too many things going on at first, but the closing act did a decent job at tying everything together. There some heartwarming moments, and the movie genuinely made me laugh a couple of times.
On top of that, the movie explores nuanced topics, and you can tell there was a lot of thought put into these themes. There are a bunch of analyses online that go more in-depth into this. I couldn't explain it well even if I wanted to, so I highly recommend checking some of them out.
As an adaptation, it was a little disappointing...
Oracle isn't there, which makes sense given the events of The Killing Joke haven't taken place in the DCEU. However, the entire team was created because of her, and she is the leader, so it feels weird having a Birds of Prey movie without her. It'd be like if they excluded Captain America from the Avengers.
I also think it's a shame that Cassandra Cain ran off with Harley at the end of the movie. Considering that she takes on the Batgirl mantle, it would've been cool to see her end up with the Birds of Prey. In terms of characterization, Cassandra's entire personality got wiped. She's supposed to be a trained assassin who's expertise is reading body language to the point where she can tell when someone is about to fire a gun. She never learned how to read or write, and her speech should be minimal (or none at all depending on when the story takes place). These traits could've translated into the movie. It's also a little upsetting they never brought up who Cassandra's parents were. I mean, Black Canary and Lady Shiva trained together, so you'd think she'd recognize some resemblance. On top of that, David Cain isn't mentioned. Her father plays a big role in her backstory and is why she wants to be a hero. Using these parts of her character would've given the writers more concepts to explore and more depth to Cassandra's character.
I have mixed feelings about Helena being white because she is portrayed with darker skin in the New 52 and Rebirth; however, even the comics can't seem to remember that, so this is smaller detail. But then it makes it weird to cast a black actress to play Black Canary. The whole thing feels iffy to me.
As much as I loved the way Harley Quinn was portrayed in this movie, I feel like, at times, they side-stepped her intelligence. Like the opening scene, Harley explicitly stated her dumb luck is what got her out of that situation, but I feel like it should've been because of her genius. If the writers actually utilized this part of her, they could've given her character more of a duality.