Following the announcements of new features for Google Docs, Slides, and Sheets at I/O, Google has announced will unpublished Quickoffice app from Google Play and the App Store in the coming weeks.
With the integration of Quickoffice into the Google Docs, Sheets and Slides apps, the Quickoffice app will be unpublished from Google Play and the App Store in the coming weeks. Existing users with the app can continue to use it, but no features will be added and new users will not be able to install the app
Refer: Removal of Quickoffice from Google Play and App Store