I firmly believe that this site was respectable until the Stratasys acquisition. Now, it's all about what they can sell for printing services and the core site which is now relegated to "community" is overrun with spammers, scammers, and hack work.
I don't know what it would take, but I'd be seriously interested in starting a new community with the same features as GrabCAD but having an application process to go through in order to become a content creator. Creators would be able to publish and share their work for free in addition to offer other work for sale.
I'm no web developer, so I can't do this myself. But I have a clear vision on what it could look like.