Most of LinkedIn seems like a scam, how do others filter the wheat from the chaff?

As a white collar professional I am occasionally required to use LinkedIn either for job searching or networking, and during these occasions I am astounded by how scammy it feels.  When I attempt to apply for jobs, about half or more seem to be fake postings posted by someone who doesn’t actually represent the company, and is probably just resume trawling to get hired as a recruiter.  Many postings are clearly sourced from somewhere besides LinkedIn because although they may have a flashy “easy apply” button, the text indicates that applications should be sent to a specific email address, or indicates that the post comes from off-LinkedIn in some other way.  And finally my messaging inbox is inundated with all sorts of people desperately asking for a 5 minute call so they can demand I let them represent me as an applicant to some company I have no interest in, or in many cases they refuse to name the company and want to represent me anyway.

I’ve come to feel that a lot of LinkedIn is a scam.  It always sounds great to allow employers and employees to find each other organically from the comfort of a computer, but without strict moderation these types of things always fall into scam territory.  

If anyone is reading this: how do you find the non-scams on LinkedIn?