It's not just the drag and drop, it's the drag and drop and edit (single) callback. Like drag a button in the middle, resize it, change the text and then right-click and start coding what pushing it does. Now a days it's not push button but mouse over, mouse down, mouse up, press, long press, triggered, etc. etc. and I have to manually find or create the right source code file linking itself to the GUI form file.

Qt and it's designer is great until you try to deploy to mobile devices. That aside, I find the non-visual components of delphi/lazarus the easiest to use when doing GUI work for the desktop. You drag a data connection, a datasource, give it a table, some filtering, connect it to a grid and the grid handles all the CRUD operations for you. Even at design time! Hard to find that ease in Qt.

PS: I really love Qt. It lets me do things no other framework can easily do. I love building performant, graphically heavy and fast user interfaces. It just wasn't built for mass-producing desktop forms that are connected to a DB.

Ish - Designer is basically deprecated and unloved.