The proponents of this holy grail of the the expert finder miss the point. The expert does not care about your problem. The expert cares about his or her problems and solving the problems of people he cares about. Does that mean that there is no hope for people who want to reach out to experts who will help them solve their problems? Yes. There is a solution. The solution is to build a relationship with people who might be of help to you and engage with them way before you actually encounter a situation where you need help.
This is a not an alien concept. We know that friends, teachers and colleagues with whom you have a prior relationship can get you a job much faster compared to strangers. This is because friends care about you. Strangers don't. So rather than wait for a tool that will find you the expert, build relationships with people so that they care enough about you to help you. You may say that this is hard. Yes it is. I did not say building relationships is easy.