It began its first steps down that slippery slope (imho) 10-12 years ago. I only log in when I want to find 'the next job'. You can safely ignore anything that says "add your CV". I usually target mega-big corps, and in that case LI always pushes you to their corporate-30min-per-application systems (keep your CV in Word for easier copy & paste). So in a way it has helped me to limit my efforts to 5-10 CVs, and a couple of them always 'lead somewhere'.
and then some flag is switched and I start getting 'a number of messages' from headhunters that (want to) waste my time. An easy way to be blacklisted by those spammers is to _always_ tell them "I ain't telling you my current $$$ or my $$$ expectations, the effing gig/role/contract has a budget+benefits, tell me what are those and I will respond". That will send those assholes away faster than garlic does a vampire. If they stay, then they mean business and they 'like' the CV enough to talk/negotiate with you.
There are some other 'smaller' ones (Indeed comes to mind) that still stick to 'find a job and nothing else'.