I think that this is a very old argument that a few (hopefully, very few) cranky misanthropes refuse to stop harping about. I prefer to think of them as "Klanimators", as such a blanket hatred of another group for no legitimate reason should, by nature, require some sort of pointy headgear.
And yet, sarcasm aside, I think I can understand from whence a lot of this came. When I started writing cartoons in the early 90's, the majority of my jobs were freelance. This meant that I was just another anonymous guy - with no specific training or knowledge of the animation process - dropping stacks of pages on some storyboard artist's table. And, good, bad or indifferent, he or she had to just deal with it...and fix any stupid mistakes I may have made because I didn't know any better. I totally get how that would piss somebody off.
I do think that, by and large, things have changed. There are more writers who have a lot of experience in this medium. Working on staff - where you're in-house and in the middle of the mix- there is an opportunity to actually...and here's the million dollar word...collaborate with the artists. I have an incredible amount of respect for the artists I've worked with - and there's nothing better than looking at a board of a script you've written, and finding a visual joke (or 2 or 10) that you never saw coming...and laughing your ass off. That's what makes this process so much fun...different people bringing different sensibilities and skills to the table.
Why a few naysayers have to constantly try to drive a wedge between writers and artists, I'll never understand.
Now, if you'll excuse me, I have to go kill another puppy.