It seems like the writer turned on Cartoon Network one random morning and decided to make an article about it.
But yeah, Johnny Test's spot is well-deserved. I think I know why so many little children like it: it seems like the show is written, designed, scored, and animated by some obnoxious seven-year old who thinks he's funnier than he really is. It's made for the demographic, by the demographic! But seriously, it's really one of the worst cartoons I have ever seen.
98% percent of the jokes are overly-sarcastic snarky quips that try too hard to sound "mature", or repeats of jokes that were funny once, in the first season. Every single line of dialogue is a variation of "Calmly stated quip or observation. YELLED OVERREACTION TO PREVIOUSLY SAID QUIP OR OBSERVATION!!!" or "Sarcastic statement contrary to what just happened!"
I personally have nothing against Flash/ToonBoom, buy Johnny Test doesn't even attempt to put a semblance of effort into the visuals. It's all terrible line-art that anyone could make with a few uses of the line tool and paint bucket in Flash in five minutes. The animation consists entirely of tweens, and not subtle, fluid tweens either, but the really sloppy jerky stuff. If shows like Jimmy Two-Shoes can pull off amazingly fluid animation with the same materials and budget, then Johnny Test has zero excuse.
And the musical cues. If one were to put the entire BGM of Johnny Test onto a CD, it would be over in five minutes. There is no BGM "music", only ten-second sound effects that are played constantly and repetitively, without end. There's the stock electric guitar wails for when something "awesome" happens. They've got the two discordant piano chords for whenever something "gross" happens. They have pretty much every repetitive stock sound effect under the sun.
I hate every single thing about this show. It's the lowest of the low, and how it managed to get five seasons is beyond me.
It's really terrible stuff.