Heh, this is gonna be easy to argue against
For one, Ash has had several Pokemon evolve, his Charizard and Butterfree are prime examples. Besides, keeping a pokemon unevolved is a smart thing anyway, because in most cases you gain your best attacks a lot faster. Would you rather level your Bagon up to level 53 to get Double Edge, or evolve them straight away, and wait until L93 before you learn it? Just one example among many
And I'll have to admit, Ash does seem like a gormless git sometimes, but that's cos they've dumbed him down from the translation of Japanese - something they do with a lot of series. Pokemon anime is very kiddified, definately aimed a younger market than Japan's audience. The typical 'oh, it's a cartoon, so it must be for kids' attitude of Americans when they see anime, so it was translated and edited with that in mind, erroneous thinking as it is.
So, albeit your original intentions were to 'bash ash', I think in this case the joke is on you. And 4Kids for dumbing down Pokemon's anime. But that's just the way things go when you think about things.