There is nothing stopping you from creating it with or without the validation of YC. You're right that just because it's been done doesn't mean you can't do it

There is nothing stopping you from creating it with or without the validation of YC. You're right that just because it's been done doesn't mean you can't do it better and get it right. Would Yelp exist if they thought -- oh, darn, Citysearch seems to have the whole market, we'll never win. That being said, you should consider starting with a specific community you know, getting it in the hands of real users, and iterating like crazy. These things can't be developed in an intellectual vacuum. Best of luck!