Yeah - I considered this. There were probably 10% of people I could tell that wouldn't lead anywhere.
Some of it was trying to not allow my own biases to cloud things. Some of it was hoping to offer a hand up to others who may not get as much attention. Some of it was wanting to just run an experiment and see what happened.
I think the best method is finding a good community to start from. As I alluded to, YC matching has not done this for me.
The other thing is to pay attention to why you didn't like a given cofounder/idea. I identified a handful of industries that just were not for me (hadn't realized this consciously previously)