If we accepted low-quality resources, then the server would reach over it's harddrive quota very quickly.
So that's one of the reasons why the site has it's standards. Other reasons are like "they just suck ass due to it's low quality" or "they're stolen from someone else" etc.
If you submit stuffs that we find crappy, we reject them.
So you have three choices after that.
1) Going apeshit and constantly spamming, flamming and ranting, which will get you banned.
2) Start learning to improve. You can do that through tutorials, search for help in the appropriate forums or look in open source maps for inspiration. You can also try experimenting with the World Editor's features yourself.
3) Don't submit at all, at least not in our database.
Number 2 (lol number 2) is the most encouraging choice as we do want more modders in our site. We just don't want any crappy stuffs.
Also, we have
this place if you wish to get some help in mapping.
I suppose this message can apply to models/skins/icons as well, since some people tend to submit their first resource and go like "This is mah first skin, waddya think?

" and hoping to get some praise for their crap.