I was recently asked by someone I very much respect to address "the" question. So I started to write the answer in a post... about five times without any luck. The "Why does a 20-something join a Reform Congregation" question.
I’ve come to the conclusion we need to change the date of Simchat Torah. Our Jewish festivals must be re-envisioned as inspirational community gatherings of joyful spiritual Jewish celebration. Every single festival needs to be a time of great community involvement and meaning.