There was a wonderful talk at UserConf a few years ago about the evolution of software products. The gist is you tend to add features to a product and have to know when to stop or roll back because in the beginning, engagement tends to go up when you add features but eventually it goes the other way.
Google's successes seem to nail this. Google's search page is the simplest anyone can imagine. Gmail is for mail, maps are for maps, Chrome is a browser.
Facebook for years seemed to buck this trend with one product to rule them all. It is your photo album, your online identity, the place you read news, where you discover events, play games, create groups, shop for used goods, find a date... There is a lot of speculation that when they wanted to become Twitter by adding news, it hurt engagement by injecting polarizing stories.