As a general rule, if you’re an engineering candidate that made a profile years ago and is missing updates and haven’t put in much description about your work experience beyond “I worked here from this date to that date”, you’re probably a good engineer.
When I look at the people I've worked with over the years, all having a blank profile says to me is that they don't care about their LinkedIn profile. I know the quality of their work and it seems to have no relationship with how detailed their profile is.
Personally, I list every project I've worked on, what my role was for that project, and the technologies used. I do that for my own benefit as well as for recruiters.
That’s how I find LinkedIn useful.