Obviously, everyone will be different but I get 2-3 emails from recruiters on LinkedIn per week. Managing them takes me about one minute per week.
Compared to the number of times where I ended up on a phone call or having lunch/coffee with a CTO, VP of Eng, architect or senior engineer, it's totally worth it to me.
My suggestion: don't cut out that option until it really becomes unmanageable. Chances are you'll find it's worth the occasional disturbance.
You have zero pressure, you can practice interviewing, network and you can make extravagant requirements. If it doesn't work out, no big deal, you like where you are. But if it does, your career can make quantum leaps.
In other words, a $10k increase in salary might not seem much but it will add up, and not only will raises compound as well but future jobs will start at a higher negotiation level as well.
Of course, spend your time wisely but I think it's really short sighted to think "I'm happy at my job, I am going to completely block out all the recruiters out there".
I understand that some people can find value from LinkedIn, but I just don't feel that I'm one of them. I attend lots of meetups in London, and participate in online discussions, and that's good enough for me.
I recognise that I could belong to LinkedIn as well as those other networks, but I get enough value out of my existing tools that LinkedIn isn't worth it.
The scummy data collection practises and the constant recruiter spam are what drove me away from LinkedIn. There is nothing pulling me back.
I've really only ever received an inordinate amount of entry level recruiters "connect" with me using the same canned email they send everyone. I thought the references feature was nice, but the past few places I've been at have officiously discouraged using the feature because of PR issues (I might personally give someone a recommendation which could then not actually represent the company's perspective of the person)
In my opinion, LinkedIn is just a very creepy and annoying service.
You don't really know that, maybe you missed out on interesting jobs and you'll never know.
At the very least, receiving recruiter emails from LinkedIn allows me to do networking and meet a lot of influential people at various companies, even if I don't end up landing a job there. It also builds my recruiter network, which is never a bad thing: if I ever need a job one day, I am planning to spam my entire network of recruiter, let them know exactly what I'm looking for and let them do the work for me. It goes both ways.
I respect deciding to opt out of LinkedIn but there is an opportunity cost to such a decision that you seem to have overlooked.