Hey common, you cannot say like that. Even if you are just browsing through GMATClub, you are learning many new things.
For ex: If you go through 1 SC question in verbal forum, you learn why it is correct as there are some wonderful explainations given by experts and woud be experts. SOme of these explainations, you may not find in your book.
If you think GMATClub is taking more time, then make a schedule. Study for some time and allot say half and hour per day to GMATClub. Get into the forum and solve questions. Solving questions posted on the forum is as good as solving them by yourself from a book. So just see it like a learning tool like OG, PR etc.
Dont forget to make contributions , this will make others know you and you can have some wonderful discussions. It is a great place you know.