I go through phases of regularly posting and just lurking, depending on whether I'm working on something that I want to promote. I wouldn't say I've had significant success, but it's helped me on some occasions. For example, I posted that I wanted to work on a startup idea and my former boss gave some really good feedback in the comments that made me realise it's not worth going ahead.

I'd say it's worth being active when you have a specific goal in mind. It requires much lower effort than Twitter because you don't have to build up your list of followers - your connections are your followers by default.

And, like everyone else says, you need to keep in mind that it's just a social media platform like Facebook and Instagram. Outrage/feel-good posts will tend to dominate the feed, so don't get discouraged when your post only gets a dozen likes. The post was still probably viewed by hundreds of people.