I don't believe being an expert & having fun at something are mutually exclusive. If one's goal is to become an expert, than I could see what you mean, but if the expertise is gained as a byproduct of doing something you like and the passion to learn more about it, that would seem to be fun.
For example, I consider you & Team9nine to be experts on the Ned rig and I am aware that both of you look at Ned Kehde as the true expert for that technique. While you two may never gain Neds expertise, that doesn't mean you aren't experts yourself. I would be willing to bet that if Ned ever spent a day in a boat with either of you, there would be something you did that made him go "Hmmm, hadn't thought of that, that makes sense". In other words, I believe experts can still learn in their area of expertise.
As Jaderose mentioned, access is a good part about why others consider someone an expert. 5 years ago, I had no way of conversing with Ned Kehde, but I did have access to you & Team9Nine. I was able to use that access to learn a technique that changed the way I fish and has influenced the other techniques I use. Ironically, while I wouldn't consider myself an expert on the Ned rig, there are people who fish my lake that do. It is most likely one of those "can't see the forest for the trees" things, if we are close to a situation, our perspective is skewed.
Back to keeping things fun, I believe that comes down to how one uses the expertise they have gained. In fishing, I have no interest in participating in tournaments (although I enjoy following them), I just enjoy the outdoor experience and don't want competition to change that experience. Now when it comes to bowling or poker, those are interests where I find the competition is what makes it fun for me. Just bowling a good game or series isn't enough, the fun comes in trying to beat someone else head to head under the same conditions. But fishing, for me, just being outdoors is the fun for me & if someone considers me an expert at what I'm doing, that is a cherry on top.