Pretty much all the material they've pushed for, uhm, almost 15 years...?
Widgets are still supported (because they work, and they are used by lots of faithful Qt customers), but QML is where they've put pretty much all their development focus since the late 2000s.
I think the point is "by whom" ? Does Qt say that somewhere? I haven't seen it. They certainly push QML, but they certainly are still activatly maintaining and improving their "old fashioned" widgets as well.
Widgets are still supported (because they work, and they are used by lots of faithful Qt customers), but QML is where they've put pretty much all their development focus since the late 2000s.