I’ll approach this a bit differently as all the great apps have been mentioned.
Greyscale mode
Maybe I’m being esoteric here, but I think this a great counter to addictive usage habits for a device. Our privacy is often compromised by our habits, and social media relies on color and dark patterns to keep us in their data collection machine.
I find that leaving my phone or computer in greyscale makes me rethink how I use my screened devices. It’s easy to say “use your phone less”, but it’s harder to do it consistently.
Also, any good RSS feed app (Feeder is great). It’s shocking how many people use Reddit as their only source of news.