YDKM – When I was in my dating years some 30 + years ago, girls had do that ALL the time. Do you honestly think we had a shadchan tell a boy we were not interested? Nobody relied on the person who set it up (if it was a set up) to do their dirty work (and that’s why it is uncomfortable – we always want someone else to do our dirty work for us). It may be uncomfortable to have to take a phone call and say, this is not going to work out (couched in a nicer way, of course), but it is part of being a mature adult. There will be MANY MANY times in life where tact and awkwardness will be intertwined, and where that young ADULT will need to face something unpleasant that has to be done (firing someone from a job, apologizing to someone whom he has hurt, owning up to a mistake he made that caused a problem for someone else), wanting to return an expensively bought item to a store), and not going out for a second date is really minor compared to those mentioned. It is good practice for the future.
If someone absolutely, positively feels incapable of having an actual phone conversation, then at the very least in response to a phone message, write a nice text message thanking him for meeting with you, but after thinking about it, that you don’t feel the relationship will move forward. Wish him well, and reiterate that it was nice meeting him. He has to be a grownup, too. Not everyone will like everyone. If they did, it would be chaos. Going through a shadchan is perhaps less of a responsibility, but it shows a lack of maturity to follow through, even when the event calls for discomfort.
If a generation ago, we were capable of taking care of our own business, why do you suppose this next generation is less capable than we?