It isn't just me, LinkedIn really has lost its way

I have constantly struggled with LinkedIn, the Facebook for grown-ups, supposedly. There is probably no other social network that is essential to be on as a serious person in business, but there is hardly any serious business that seems to take place on LinkedIn, except recruitment.

So help me out here. Am I doing something wrong with this service? I posted a fairly existential question about LinkedIn on LinkedIn recently and at first it mysteriously disappeared. Censorship I think you can safely call it.

Then, when I edited out any reference to LinkedIn, I posted it again and from my 500+ connections I got two replies. Then I remembered why I rarely checked postings, posted, or even knew such a service existed.

The frustration started when I kept getting random people agreeing to connect, who I don't recall inviting. Maybe I invited then because I mistakenly clicked on the Gmail account button when I was trying to cross-check contact lists I have built up. That, or they spammed everyone in my email account? 

For three years now I've bemoaned the faulty user experience on desktop, tablet and app - they are so different that it feels like another service entirely. 

We went to see Allen Blue, one of the founders a couple of years ago. He was excited then about some big changes and opportunities coming down the path. Just as he did in this video on the Guardian site. All that stuff about channels - nope, me neither. Do you know what, I'm still waiting for the great leap forward. 

I keep up my profile. I see why that is important. But how it helps the world's professionals beyond helping headhunters find people jobs is still a mystery to me. 

It pretty much fails in its social mission too. I moderate a couple of Groups and have joined a few more. Who posts in Groups? Who other than recruiters and SEO hucksters really uses it as a social media platform to engage and use as a business tool?