For the time being, I have no plans to change our federation policy. I realize this is not what you want to hear, and I'm sorry to disappoint you. It's just not a goal for lemm.ee to curate external instances for now.
There are probably many instances out there that have horrible content (content which would get users banned if they posted it on lemm.ee), but vetting instances and maintaining a defederation list is a big effort, and I believe this effort is much better spent elsewhere.
I've stated this in many other similar threads, but let me also reiterate here: the above should not be taken to mean that lemm.ee is some bastion of free speech absolutism. Users or communities breaking rules on lemm.ee are dealt with. Also, we do reserve the right to defederate any instance which starts causing problems for lemm.ee on a bigger scale (so in cases where banning individual users is not effective).
I realize this is a topic where it's impossible to make everybody happy, because each person has their own view on what should be federated or defederated. At the end of the day, for anything that's not illegal or directly hurting lemm.ee, I believe it's best to leave these decisions up to users - you can make your own choices with which users and communities you block, and I'm certain that soon you'll have the tools built in to Lemmy itself to make the same decision on an instance level as well. And if that doesn't work for you, then there's always the possibility of joining a different instance with a different approach to federation.