I don't get it. I get why he doesn't like Disney and anime - neither is as zany as the kind of animation he likes and makes, and he doesn't like pathos scenes. But why the hell does he like Hanna-Barbera? They're the guys that ushered in The Dark Age of Animation by cheapening animation to a painful extent. Sure, a lot of their early work was pretty good, but the animation for everything they made up until the early 90's is pretty much abysmal, and most of the stuff they produced from the mid-70's all the way through the 80's was some of the worst animation ever produced. What gives?
Although Hanna-Barbera's television animation lacked fluid movement (and John himself admits this), the characters had very unique appeal, design, colors, personality, and voices.
That's actually something you can see evident his own work - Ren and Stimpy don't move a lot, but they have strong poses and design, like HB cartoons.
So...exactly how popular is he with other independent animators and animation companies? A question that always seems to come up at every animation film festival I've been to with a Q&A segment is, "What do you think is the most important thing that makes a good animated work?" And every single time, they unanimously say it's the story. John K., from what I can get, not only does not think this way, but seems to want to put an end to all animated works that put the story first. This leads me to believe that, aside from his followers (whose numbers I can't estimate with any clarity), he is a pariah even among animation people.
No matter what you think of his beliefs, he's an influential and celebrated cartoonist. Ren and Stimpy was pretty much the definitive Nicktoon, the show that gave them their edge, so without him '90s cartoons would have been much different. Most animators just look at the strength of his work rather than his opinions.