The decline of welcome "Check out this link" messages is at least partly because everyone is getting the same links from the same sources at any given moment.

If you found it on a surface-level subreddit, a major Instagram account, a major news site, or a big podcast chances are decent that the content in question has already been seen by a fair number of people, and to them, seeing it again has no additional value.

I see this play out hundreds of times in real life where the conversations start with "Did you see...? and "I was listening to a podcast about..."

Part of it is that most links, even when the content is good, come with some amount of pain in accessing it. Cookie banners, in-line ads re-flowing the content, pop-over ads, "subscribe to my mailing list" popups, donation begging popups, long-winded articles needlessly stuffed full of SEO keywords, auto playing videos, and most websites so full of all this stuff they jank out my phone and make it heat up.

I remember the web as fondly as you do. I spent hours on StumbleUpon just finding cool websites. But nowadays even if the content is just as good (it rarely is), the websites are just so bad.

Maybe its also because good content is more frustrating to actually get to. Compared to a decade ago there's a lot more friction on a first visit to a site. All the marketing pop-ups, paywalls and surveillance consent boxes are a hassle and page load times seemed to have gotten worse. Maybe we've been gradually conditioned to avoid those frustrations unless its really worth it.