I started a non-profit a couple years ago that helps young girls (generally 18 and under) with a specific type of problem. I don't want to get in to the details, but point is...some of their situations are ones I've been through, some are things I haven't. And I know for a fact I/we help all of them, even the ones who's situations are different than my own.
Things in here are too specific if we're talking about mental/emotional trauma. I don't need to have gone through the exact trauma someone else has to help them deal with that. We've all struggled.
Oh, but I don't think there's anything wrong with someone going through a divorce giving marriage advice. EVERYBODY gives advice they don't follow themselves, everybody. I don't care how old someone is or how much experience they have, outside perspective is always different and often clearer than it is on the inside. So not following through in your personal life, doesn't mean you don't know what should be done, IMO.