can't I block communities on instances I'm not logged into?
I have a Lemmy world account. But when browsing all. I see communities I'm not interested in clogging the feed. If they are from another instance is there no way to block them from appearing?
You asked for a way to block communities from other instances.
Now you can go through all communities on all federated instances and block them one by one. I'll surely be impressed by your endurance if you manage to do that.
That's what "all" means, "all communities everywhere". If you only want to see groups on your instance, set your view to "Local", or even "Subscribed" to only see groups you have subscribed to.