I disagree, and I've re-watched the entirety of the anime in the past couple years. BW is the worst offender by far, but there were multiple times where Ash seemed less competent than he should be, which I consider to be a reset if only a minor one.
Edit: Perhaps "regress" is a better word? Either way, he's rarely quite as competent a trainer, or person, as he was at the end of the previous series.
Edit2: Hell, the reason this and preventing him from aging bugs me so much is precisely because I do watch the anime, and it drives me mad x.x They do character development episodes and stuff and it ends up being thrown out the window, until they want to pander to nostalgia and bring back old characters or Charizard. And it'll be incredibly annoying if they pull that after XY with how much progress they've made.