I may sound like a broken record, but flying is well done in Solasta and I wish it would be implemented in BG3 too.
- Not everyone is flying. It requires the fly spell or the creature can fly itself, like a bird for example. Fly spell requires concentration so you may fall to your death if the caster takes damage.
- Flying does not make immune to melee attacks. You can attack any creature in range and flying creatures provoke AoO unless the creature uses disengage.
- Flying creatures do not suffer under ground effects when they fly. Creatures with the ability to fly can still walk and then they are hit by ground effects.
- Fly = big jump looks bad in BG3 and the merge of jump and disengage makes it worse.
- No need that everyone flies at 20 feet (20feet above what?) The advantage of fly is free movement in all 3 dimensions. Imagine you fly over a house, does it make sense that you fly 20 feet above the street, then you jump up and fly 20 feet above the roof and then you jump down and fly 20 feet above the street again? I do not think so. Of course there needs to be an upper limit because the map of a computer game cannot be infinitely high.
Main problem for flying would be selecting an empty space in the air as target, especially without the grid structure of Solastas maps.
I do understand that it is very hard to implement flying properly. It would be nice to have, but Id rather have it not at all than the devs add it in a bad way.

Prof. Dr. Dr. Mad S. Tist

World leading expert of artificial stupidity.
Because there are too many people who work on artificial intelligence already