. . has been, "How could birds have evolved wings when only a fully evolved wing is of any use for flying?".

Recent studies of immature chuckers show non-flyable wings are still extremely useful. Chuckers that can't yet fly flap their wings in a manner to generate reverse lift to hold them against the ground. By so doing they can run up embankments so steep predators can't follow them. In fact a chucker that is almost ready to fly can run straight up the trunk of a tree.

Then, when the wings are strong enough, they reverse the action and use them to produce lift.

Velociraptors were probably damned hard to get away from.