There are already dozens of decent feed aggregators, and I’m not interested in Lemmy tacking on functionality that’s superfluous to social media. https://en.wikipedia.org/wiki/Comparison_of_feed_aggregators
Or do you mean follow or block posted links to sites? That functionality already partially exists at the admin level. We can block posts of URLs to specific domains. https://github.com/LemmyNet/lemmy/issues/4514
There’s already a ticket for per-user URL blocklists: https://github.com/LemmyNet/lemmy/issues/4689