I use Reddit and am blissfully unaware of such subs.
As to "designed to be addictive", you are literally using that as a lazy, pejorative surrogate for "designed to be rewarding/enjoyable".
Understand that almost every part of your life is "designed to be addictive" by that sloppy trope. HN is "designed to be addictive" by putting the most interesting stories on the front page. Netflix, Facebook, Starbucks, McDonalds, Movie Theaters, Parks, Conservation Areas -- Designed to Be Addictive. It is meaningless prattle, though it's usually leveraged to dismiss things Other People enjoy.
I don't care that you use reddit and are unaware of what content is on it. I could not care less.
The tik tok algorithm is designed to be addictive. It sounds like you agree but are trying to obscure that fact by throwing examples of other popular products.