Facebook algorithm shows your content based on your interaction with your friends. So if you do not like / comment for a while your friends may not see your posts too. May be that is why they are not being able to like / comment on your post. That does not mean they are inactive. You can try to visit some random friend's profile and check your newsfeed afterwards. You will see their posts on your newsfeed. And about the mass delete, I suppose there is no such bot and I think it is not a good idea to delete friends as they are not liking your post/comments.