GWT was replaced by the similar J2CL and is used for GMail, Inbox, Docs, Slides and Calendar.
Re:Four Eras of JavaScript Frameworks
by cmrdporcupine on Wednesday April 27, 2022 @04:20PM
(#31185223)
I wasn't on the gmail team but my understanding from friends that were is that the Java transpilation in Gmail is for the backend, to share model and business logic, not the frontend.
GMail, AFAIK, never used GWT for its UI
In fact when I got to Google in late 2011, I believe the only thing I could confirm using GWT seriously was some display ads admin tools.
GWT was awful. And not really used inside Google much.