Sure, but now this system has a dependency on the “centralized” lemmyverse.net service. And also your instance now has to receive and store a copy of almost the entire network’s content. Lots of instances are already struggling to sustain the load, this would make the problem even worse.

If a single instance decides that it can sustain the increased load and doesn’t mind depending on lemmyverse.net sure, nothing’s stopping them. But it shouldn’t be the default behavior for all instances.