I feel like a lot of the "it's for children" crowd don't watch a lot of cartoons today, or didn't get a lot of them back in the older days, either. It's never something that gelled very well with me, and I feel like you can't help but shudder at remarks like these if you happen to be a writer, director, voice actor or animator (or any other position) for cartoons.
That's like saying all romantic comedies are for middle aged women. Why not generalize everything?
Even as a kid, I could tell when a show was just pandering to me. The only difference is that I didn't care if I liked the characters. That hasn't changed too much, but a script has to work for me to keep my attention. And if you're aspiring to work in the animation industry, you kind of have to stay on top of popular children's shows and evaluate them. Unless you're doing an early childhood show with a demographic of 1 to 3, it seems like you'd be doing a service not to sell your market so short. Children are a lot smarter and more creative than they were even 10 years ago, I don't think people need to talk to them like they're slow. I hated it when grown ups patronized me.
As for Pokemon, I think a lot of the trouble lies in line repetition, which sometimes couldn't be helped, annoying as it was, like whenever Meowth had to translate Pokespeak ("what? You want to know why I just asked you why you asked me why I asked you for the time?). Honestly, there was nothing wrong with the subtitle method in the Giant Pokemon episode from the first season. It didn't make them less mythical. The other problem is the obligation to fit dialogue into mouth movements. I always felt like that was one of the downsides to dubbing any anime. Having to either cram as much as possible in few mouth flaps, or drone on and on (usually without a pause) when the character could've said the same thing in fewer words because the mouth keeps moving.
Then there's that extra mouth flap that just comes out of nowhere they have to account for, which is awkward. How can you forget lines like "Don't you understand? Those Pikachu are scared of you. Ash." from Pikachu's Goodbye? Wait, how do I remember lines like that?
I think that's more annoying than not being written with smarter humor, but I suppose it comes with the territory.
Other Stuff That's Totally Uncool and Not Worth Your Time!
This is true. I remember watching Pokemon back when I wasn't that mature, and I remember that I enjoyed it. Now that I've mentally grown, I think that the dialogue is too childish, and that I'm getting too old for the anime. It's all about our perspective. As a child, we loved it, and as a growing human, we change.
And guys, just chill for a sec. Everyone has their own opinion. If one thinks the dialogue is bland, and one disagrees, that isn't enough reason to start a war. I personally think the dialogue is bland, and the creators of the anime could do a much better job on the script, but at the same time make it safe for children. As I said, everyone has their own opinion.