Pony Creator has basically been around since the beginning of the show. It was pretty unpopular even back then.
It's very...generic. It's like giving someone a bunch of differnt stencils and letting them piece together the pony. There's no heart, no creativity, and no love in it. When you see true art, you can see the work and labour the artist put into it. Like so many of people above have already said-Pony Creator should be used like a stencil. For you to start with as a base-but for your imagination (or whomever the artist is), to make it personal.
Because there are a lot of crappy oc's made in pony creator. And a lot of people see it as pazy. Granted I feel you as I can't draw either.
There are many anatomy errors in the pony creator that makes the end product look wrong. The expectation is that if you care about your OC enough to put effort into him/her, you'll put effort into drawing him/her yourself. As for why people are rude to those with "Unoriginal" OCs? They've been told it's fine to bully dumb kids trying this whole fandom thing for the first time. That's what makes people like that jerks.