Everyone's insights are valuable, even if what you have to say is similar to things that have already been said. People see things different ways, and people explain things different ways.
Personally, I'm not bothered by lurkers - there are a number of forums where I just lurk, preferring to read and learn but not feeling like I have much to contribute. But it's important to realize that we may not always realize how valuable our contribution might be to someone for whom our thoughts just happen to resonate.