That's not how it works. For food, one person enters the data from the label on the back, other people scan the barcode with their camera and it's added as cons

That's not how it works. For food, one person enters the data from the label on the back, other people scan the barcode with their camera and it's added as consumed. That's how MyFitnessPal works, as well as alternatives that use OpenFoodFacts under the hood. For other types of data, you have other aggregators that are used for a specific use case (Pocket for Articles, Last.fm for music, Trakt.tv for shows/movies, Goodreads for books, various device trackers for steps/heart rate/sleeping patterns etc). Then you use tools that combine those things together, like Exist.io. Alternatively, you go through a middleman route like Zapier/IFTTT/Integromat/NodeRed to not have to fuck around with each API separately. Then you use a system that visualises it all. Granted, there are some blind spots that will make you have to enter the data manually (example: with Netflix you have to manually download a CSV, and it only includes the title and a date, not the time of the day nor the watch time), but that's really not that time consuming. It takes me about two minutes per day to fill in the missing fields in my system, and I spend a few hours every two months or so fucking around with the data to find some correlation that I simply wouldn't be able to find otherwise.