I'm not addicted to Tumblr (at least I don't think so) because it doesn't provide any real emotional engagement

That's an interesting definition! I think it works differently for me, probably because of the infinite scrolling. My answer to "is it addictive?" is more related to "am I still on this site even though I would rather be doing something else with my time?" and apparently, even without much emotional engagement/friend interactions I can still get into that state. I have to use a browser extension to restrict how much time I can spend there.

I hope you can peacefully enjoy the pretty now you're back and free of Reddit!! :D