Expertise varies. Everyone is per say an expert at something they have mastered, although it may not be in the realm of model aeroplanes or a segment thereof.

A good number of experienced modelers I've met, will admit they don't know everything, but will help with that they know. There is a certain humbleness about someone who knows his subject really well, and does not need to justify himself. Those are the type of people I really enjoy associating with, because they have a wealth of knowledge to glean from.