I've always considered linking perfectly fine, but what to me is shady when platforms start to summarize or preview content of the link to the point where that functions as a substitute for the site.

There needs to be a distinction between reference to content and the content itself. When platforms start to profit from other people's work without their consent that shouldn't fly. Google search's primary purpose is to make links discoverable and I don't think anyone ever took offense to that. But in recent years companies have started to deliberately blur that line by showing more content upfront, essentially to turn themselves into a middleman and choke content producers. It's perfectly legitimate to not allow this.