Yeah, I think we'd all prefer a site like LinkedIn that somehow manages to avoid "recruiter spam" and all that, but for me personally, I can tolerate a little recruiter spam... and hell, every once in a while I get something like that, that is actually interesting enough to pursue.
I get useful information about available jobs in my segment of the industry because LinkedIn knows what kind of work I do as opposed to just "he's a programmer." The recruiters who contact me from LinkedIn are looking for people in a specific domain, as opposed to "knows language X and framework Y." I consider that to be a hell of a lot more useful than the usual email job spam.
I also get to see if I know someone who knows someone else that I might want to be introduced to. It's a lot harder to do this on your own without a stack of cross referenced rolodexes.
That said, I think LI has value even if you're not interested in founding a startup or whatever. I mean, I'd rather keep a (more or less) master "rolodex" of people I know and have some connection to, on LinkedIn, than have to spend all sorts of time trawling through old email lists, Quora, Meetup, SO, etc., just to find somebody's info. But that's just me.
You have cultivated other networking channels. Great! But I would like to point out to you that now you make the basic cognitive fallacy thinking that anyone who is not doing it "your way" is doing it wrong.
