I don't know. I like LinkedIn. They've made some great changes in just the past few months. And EVERYONE in the business world uses it. It doesn't seem to be too bothersome to me. I haven't noticed it asking me for anything except to recommend skills for others, lately. And I am happy to do it. A lot of people have done it for me. So I'm happy to recommend them for things I know they're good at. Otherwise, it seems to be just a simple place to keep all your business networking contacts in one place. I like it. Very simple and professional.
I wish your son the best. But trying to get people away from LinkedIn will be an immense undertaking. People have been trying to invent a better eBay, Facebook, Google for years. Spent billions of dollars doing so. But once someone gets that much market share, it's hard to get people away from it. People seem to stick with what they are familiar with, whether or not there's something better available.