A proper flight system would also require a good camera control system, which BG3 is also lacking. Other games that use full 3d spaces have controls that allow you to move, position and to raise and lower your camera viewpoint - this in turn allows you to isolate a position and then slide up and down on the vertical axis with easy precision. It's very straight forward - BG3 is crippled in this respect because it is built on the hacked-apart and re-cobbled game engine that couldn't handle it, and Larian decided not to address this problem when making this brand new game for which they touted unparalleled verticality in their tactics. (BG3 is in fact entirely 2d in its logic - AoEs explode as flat discs that don't affect anything above or below them, even if that thing is right next to the detonation point.)
