I rejoined LinkedIn a while back after quitting years ago. I've since had numerous connection requests from people I didn't know who didn't even reply to a short, friendly message back. I joined some popular groups related to my professional interests, and their content turned out to be close to 100% bad-subreddit-quality self-promotion. The valuable connections I do have on LinkedIn invariably originated with some encounter elsewhere and then one of us looking the other up, not through LinkedIn itself. LinkedIn has produced, to my knowledge, 0 useful opportunities either for me or for someone in my network through me. Not a single one, ever.

Meanwhile, I've been an active participant in many other online forums for decades, from old-school Usenet to HN. The opposite of everything I wrote above about LinkedIn applies with many of these other forums: I have enjoyed countless worthwhile discussions with interesting and/or professionally relevant people, replies or private messages I've received have been genuine and relevant, from time to time useful opportunities have been found for me or someone I was talking to, I've often found external material via those forums that was interesting or informative, etc.

So am I bad at online networking, or is LinkedIn just a bad forum for useful online networking? IME, it's very obviously the latter, and that doesn't appear to have changed much during the extended period when I wasn't using it. The more I write here, the more I think it's time I got around to deleting that account (again).