The thing is that say i want to see all the pickle content across the lemmy-verse, i want to just be able to subscribe to an umbrella "pickles" category and get all the c/pickles content from any instance my instance federates with without worrying that i missed a community or something. If there are 20 groups but i only know of 1 or 2, odds are that i'll miss the biggest ones with a bunch of pickle content that i want. And I don't want to have to manually go through, search for all the biggest instances, and subscribe to each pickle community one by one. Plus, say a new instance is started and it's pickles community blows up. I'll miss it because i already searched through and subscribed to all the pickles communities that were available when i joined. I'd rather default to subscribing to all the c/pickles communities my instance sees, and then if one instance is posting stuff i don't want to see i could manually exclude them

Tldr I guess it depends what you think will take more effort to do manually. I think having to manually find and subscribe to every community i want from across the lemmyverse (and periodically run the search again to find new communities) would be way more work than subscribing to every c/pickles my instance can see and manually excluding the instances or instance-specific-communities i don't want content from