I get the feeling that all these "digital detox" apps, if they aim to scale and make more money, will do so by "whitelisting" certain popular apps by making access to them relatively easier, bottlenecking the competitors.
Let's say it's the future, 10% of phone users have some version of this on their phone. Snapchat pays them 10 million to reduce the penalty for using Snapchat auto-suggest Instagram on the block list.