Other than the fact that we need another new token female companion every series.

Serena hasn't even had a single real battle since the saga began. Her pokemon has attacked TR a few times, but she's never actually battled a trainer. She is going the longest without capturing a second pokemon, over 40 episodes if the new Japanese opening is anything to go by/

Serena is probably the most utterly incompetent Pokemon trainer we've ever seen on the main cast. She treats her pokemon more as a pet than a Pokemon. It's like she's only there to be a bland girly love interest to Ash and nothing else. She seems to have no interest in battling at all, or doing anything Pokemon related.

I don't know why the female leads in the anime have been handled so poorly since the end of DP. I thought Misty was fine for the first token sidekick, May and Dawn were probably handled the best....but ever since Iris and Serena they've dropped the ball. Have the writers just given up on female characters after introducing so many?

There is nothing wrong with Serena's character. She's gotten some focus, but right now compared to Clemont she isn't getting as much because Clemont needs to be very developed in time for the gym battle Ash will have with him. She'll likely get a significant amount of focus in the 2nd half of XY, and yes some of that will relate to Ash, because unlike past female companions it seems they are definitely going somewhere with AmourShipping. She might indeed be Ash's future wife, and the anime itself may even be ready to wrap Ash's story up. After their experimentation to reset Ash in Unova failing and the increasing amount of specials with other focuses, the anime might be ready to veer in another direction. Though Ash probably wouldn't be gone all together.

And yes, she hasn't decided on a goal yet, but she does have a rival now, and I find it more realistic that she hasn't decided on something. The slowness with Serena could even suggest she sticks around for Gen 7 or beyond. We don't know yet. Just reserve judgment on Serena until we're a little more then only two gyms into the series. And chill out on your raging sexism.