The thing with starting a startup is that VCs look for trust. It doesn't matter if they like your idea or not, if they don't trust you, you aren't going to get your hands on their pot of money. Perhaps YC just felt that you couldn't pull it off that well, and then when the next team came along with apparently the same model, they felt the opposite this time around.
You could also be dealing with a case of having an idea that's too early for its time. Look at how much of a hard time Google had getting angel investors. If you feel that you have a solid idea, do it anyways. If it's as solid as you think it is, and you pull it off well enough, they'll come knocking on your door later on down the line.
Creating a startup is all about taking risks, and if you aren't willing to take a risk then don't travel down that path.
You could also be dealing with a case of having an idea that's too early for its time. Look at how much of a hard time Google had getting angel investors. If you feel that you have a solid idea, do it anyways. If it's as solid as you think it is, and you pull it off well enough, they'll come knocking on your door later on down the line.
Creating a startup is all about taking risks, and if you aren't willing to take a risk then don't travel down that path.