Technology

I think the brave explorers are still here, they're now just vastly outnumbered. The early Internet was full of those explorer types because they in particular tended to have enough interest to overcome the hurdles of getting on the Internet: namely computers being expensive and somewhat difficult to use. The early Internet was more accessible to intelligent, innovative users, and it reflected its user base. Many got online to explore and continued to explore and innovate once there.

Now millions have a user-friendly computer in their pocket, so practically anyone, even flat earthers, is capable and intelligent enough to use the Internet. Most are attracted not by exploration but by access to specific services that have been advertised to them, especially social media. The Internet continues to reflect its user base, but the user base's composition has... changed. Let's just call it changed.