I don't know enough about Qt to know if you're right or wrong, but I know enough about game engines to know that whatever Qt is or isn't, it doesn't negate the usefulness of game engines.
I have written a few 3D applications in both Unity and Unreal, and I can tell you that the cross-platform build process with those is impressive. I can package an app for three different platforms and get pixel perfect equivalent output and the exact same behavior on all three platforms without any trickery at all.
Qt probably also does this, and that's great! Qt existing doesn't take away from the utility of game engines, is all, nor the reverse.
I have written a few 3D applications in both Unity and Unreal, and I can tell you that the cross-platform build process with those is impressive. I can package an app for three different platforms and get pixel perfect equivalent output and the exact same behavior on all three platforms without any trickery at all.
Qt probably also does this, and that's great! Qt existing doesn't take away from the utility of game engines, is all, nor the reverse.