Way back in August 2016, Google announced that it would be shuttering the apps section in the Chrome Web Store. As the company had stated in a blog post, this was one step in a process to shut down standalone Chrome Apps that nobody really downloaded from their browser anymore. Today Google followed through: Chrome browser users can no longer access or install apps from the Chrome Web Store.
By early 2018, Chrome Apps already installed in Google's browser will no longer function. Chrome OS users, however, will still be able to access them for the foreseeable future. And folks just using Chrome to surf the web will still be able to download extensions and themes.
Instead, Ars Technica points out, Google is pushing developers in a different direction for desktop: Progressive Web Apps (PWA). The hybrid online-meets-installed software launched earlier this year on Android, essentially bringing app features to websites. Google is reportedly estimating a mid-2018 release for PWA on desktop.