Ash is definitely a much better trainer now than he used to be. Sure Pikachu still loses, but Ash's pokemon teams in the newer sagas have been excellent. He finally looks like a powerful trainer with mostly evolved Pokemon. Its just that at the start of every saga he goes back to a new team, so it takes a while for him to get strong again.
Much in the same way of the female characters, they start off as beginners/weak but get progressively stronger as the saga progresses.
Too bad with Misty they didn't develop her much. Her team was incredibly weak and as a battler she was pretty lackluster, relying on Psyduck got win with a headache rather than battling properly. Misty could have been a great battler, instead she was nothing more than background fodder holding that Togepi in her arms.
I think Iris will be Misty done right, and show what she could have been like.