To be a model, it it all comes down to how much you want the things you want, and what you do to make them happen. There isn't a website that can make you a model, or person that can make you be something without your own true effort.
The entertainment business has a lot more to do with your own effort, than being discovered. You have to do your research, make your marketing material, photos, headshot, put together a resume and avoid the scams, and submit, submit, submit your photos out and market yourself.
The web can help but I find it best as a research tool.
I do not think you will be discovered on a social modeling site, even though every day there is a new one booming out of the wood work of the world wide web, but I do think Google is the best marketing tool for an aspiring model, new model, or actress.
You can Google if an agency is a scam
You can Google everything from printing options, to agencies to submit to, you can research photographer's work, and also google brands and magazines you might want to submit your photos to, and I find Google to be such an important daily tool for marketing yourself as a model. Not marketing yourself soley on the web, but using the internet as a tool for answers. Especially since starting to model can be a very lonely dodgy business to learn.