oomis-
I agree with what you said- except for the part about going out with the girl one time. If you are sure it is not for you, why waste your time and hers? “
Because getting to know someone is NEVER a waste of time – he/she might not be for you in the final analysis, but by getting to meet that person, you might see someone who while not YOUr bashert, might be perfect for your sibling, cousin, best friend, neighbor, etc.
That’s how my nephew met his wife. She reluctantly went out with his best friend when they were set up by a mutual friend, and they immediately knew they were not for each other, but the friend also knew she was right for my nephew (and boy was he ever right about that!).
Meeting new people is only a waste of time if you make it a waste of time. At worst, you have most likely spent an hour or two of your time with someone not suitable for you. At best, you have unexpectedly found your zivug. Unless the girl absolutely refuses to go out with a boy who is not learning full-time in Kollel and he is already getting his Masters, or he is 5′ tall and she is 6’2″ AND IT BOTHERS THEM, or unless one or both of them are really obnoxious people, all dates should be seriously considered before being rejected, IMO.