I think young people don't run because they are not sufficiently informed about the procedure. They have a lot of information about how to vote, but the process to run for office is still quite long. They are probably not sufficiently educated on the matter. I come back to the need for a citizen participation course. That might be a useful way to solve the problem.
Another barrier is the lack of experience. Many young people don't run for office because they think they are not ready to sit in the House of Commons because of their lack of experience. That is certainly a second barrier. The lack of experience does not help.
I had a third point in mind, but I can't remember it right now.