I think people are aware of when they're Doomscrolling[0]. Do they need their devices to remind them of excessive screentime? That depends on what info they're consuming. I deliberately follow and subscribe to positive and uplifting content, and people. There are plenty of groups on Facebook, and lists on Twitter that have nothing but inspirational messages and content to make you Think Different™ about your life. I have two news apps on my device that I check daily just to keep tabs on current events. I deliberately train my feeds not to have news-type content because once I've read the news, I don't need to see it popup in my feeds again throughout the day.