I've been using LinkedIn for years. I'm one of those cynics who loath all those "inspirational" and "leadership" posts, but there's more than that. I've met some people who tremendously boosted my career. I've met people who later became friends and our kids play together. I did meet a lot of incredible people in various jobs who I wouldn't have met otherwise(e.g. CEOs of very large companies- I'm just not in those circles to meet people in such positions). I'm often involved in interesting and challenging discussions on various technical and other topics.

The main point is that everyone can use it in a way they want to.It's perfectly fine to become some influencer if that's what one wants. It's equally fine to have 45 connections with people who are really good in what they do and perhaps exchange 5 messages a year. It's massive platform, so it's inevitable that there will be lots of crap out there,as in any other large forum without very strong moderation.