Some people really arent interested in Theology. Most people who are OTD probably fall into that category
I think thats part of the problem on both sides. If you love Yiddishkeit its almost unfathanable that someone has no interest or little interest in it.
If a bocher says he doesnt like learning and hates Gemorah, People cant belive its true.
A place needs to be found for such people and until we are admiiting that such a thing exists, there will be no solution (Perhaps there is no solution and drop-outs are just par for the course) and we have to live with it