I like Kira quite a bit. She does get better as the show goes on. Yes, she's angry, but she has good reason to be. She grew up with her people as slaves, the most attractive women used sexually by their masters, her planet's resources stripped, etc. We also see Kira as compassionate and nurturing, with her as a surrogate for the O'Brien's, her close friendship with Ziyal, etc. She grows and even learns to care about some Cardassians, like the man who thought she was his daughter. I did think the romance with Odo was a misstep.
I also thought that a male Dax would have been interesting, especially if he'd been gay as Trek still never really explored that directly. But I do get that the show needed a stronger female presence too. That's their fault for only having two female main characters in a pretty large cast though. They'd have needed to make it clear that the new Dax had always been gay and this wasn't a result of the symbiote.
I can see where Jadzia and Ezri both didn't really have the gravitas to be convincing of having so many lives under their belts. I did like both of them a lot, and Ezri covered new ground with her identity crisis as she was initally uncomfortable being joined where Jadzia always embraced that.