I honestly don't see what's so bad about Powerpuff Girls. It's just one of those shows not meant to be taken seriously, like Spongebob or Fairly Oddparents. Nothing wrong with that.
My fav PPG character was Mojo Jojo. He was just hilarious. I love the way he talks, the way he acts, etc.
One thing I do like about the show other than characters is how uniquely they seem to portray superheroes and villains. The fact that they don't always fight each other (even going as far as trust Mojo Jojo to be their babysitter or go into his lair to get their ball back despite being mortal enemies) helps make the show more unique and stand out more.
I guess it's a show you can like or dislike. Personally I liked the show and I disagree with the statement that it's "bad".
And the whole "villains don't do anything while the girls beat them up" is inaccurate, in my opinion. It's not that the villains purposely don't try; it's that they can't. One must realize that these girls possess both superspeed and superstrength. The villains don't have superspeed (and in many cases, superstrength as well). The villains don't stand a chance. They wouldn't have any time to attack the girls back. They could take a swing and the girls would be gone and punching them from another side in a matter of seconds.
When the girls were pitted against their male counterparts, the Rowdyruff Boys, they did not get pummeled as easily as the other villains. Because they had superstrength and superspeed just like the girls, they had a better chance at countering them. The only reason they were destroyed in their first creation was a flaw in their design (the whole kissing them causing them to explode).
And it's not like the villains never gain the upperhand at some point. For example, there's an episode where Mojo Jojo tricks the girls into thinking he just wants to be part of a slumber party. When the girls and their friends go to sleep, Mojo Jojo grabs the antidote for Chemical X and pours it on them, causing them to lose their powers. That was pretty clever of him, I think.