I know what you mean. There are a lot of times when I think about replying to a tweet I've seen, but decide not to because it's from several hours before. Or if I tweet when none of my followers are on, I don't get any feedback.

In the end, I think I couldn't identify with the culture of tumblr as a whole. The way I want to do fandom and interact with people on the internet is not the way fandom works on tumblr or the way people interact (when they interact at all) on tumblr.