I have a highly optimized LinkedIn, yet I don't really spend a ton of time on there. I log in once or twice a month, answer messages, and do a few things. Maybe make a post once every 2 months or so. Nothing crazy, yet my profile is very well optimized.
And this is why: Everyone looks at it. Far more people then you would expect.
I can't tell you how many meetings I have gone into where I walk in and see that everyone at the conference table has my LinkedIn profile up on their laptops. They knew they were meeting with me, had no idea who I was, so they looked me up on LinkedIn right before. Its my introduction and sets the tone for a meeting or presentation. This experience is not only in the professional world either. I recently (in my mid-30s) decided to go back to academia to get a PhD and now I am encountering people in academics who use my LinkedIn to learn about me when I reach out for academic or research assistance. When applying for stuff, presenting at conferences, all of it uses LinkedIn as the central way to communicate your identity. Having a nice profile helps me set a positive first impression that helps me gain more responses.
Also, I can't fail to mention that recruiters use LinkedIn as a search tool. Not every recruiter is worth your time, but the right ones certainly are worth it and LinkedIn helps connect you with more of them. THey also use your LinkedIn when communicating with their clients. Almost every job interview you do, you can assume the hiring manager and interviewers have looked at your LinkedIn profile before meeting you. Most have probably looked more closely at your LinkedIn profile than your resume.
Curating a LinkedIn profile is not that much work. Maybe 30-60 mins per month is all it takes if you have a lot happening and maybe 1 hour per quarter for everyone else. Its not a huge commitment, and yet the gains in my opinion are far greater than the small amount of time spent on it.
I don't care if people want to hate on LinkedIn and say its stupid. If anything that benefits me, because it helps optimized profiles stand out. Maybe theres a few people (like the parent comment) who have an aversion to LinkedIn for some reason and will look down on someone with an optimized profile. But I truly believe it offers far more value than it detracts. The people that look down on it are usually people that are not in any position of power anyway or they are a micro-minority.