Ranged characters do have lower hit rates at close up combat. Also height in reality would provide advantage / Disadvantage and applying as such makes sense. As for Flanking also it is a good balance. Ranged characters do have disadvantage with ranged attacks in close combat. If you look at % to hit its lower when the target is close to you. And thats from the perspective of someone who prefers melee combat. Its is used in actual play and it makes sense to have it in game from the perspective of every other game with similar combat. Necromunda / Xcom apply advantage to characters on higher ground. In real life higher ground also gives you an advantage as does flanking. There is a reason those tactics are used in combat in real life because its hard to defend against someone attacking down towards you like wise its hard to defend when you have 2 opponents on opposite sides of you attacking you because your attention has to be in 2 places at once. Those 2 factors make sense why the attackers with that advantage against you would have advantage on attacks against you. 0 Complaints at all about the feature as it makes sense and is part of actual game mechanics.
There is a difference between "an advantage" and the D&D mechanical term "Advantage." I don't deny that high ground can make ranged attacks easier, but high ground giving the mechanical capital-A Advantage is too powerful.
And flanking isn't in BG3. Flanking would be better than what is present now, which is just you get Advantage if you go behind someone. So you have 0 complaints about something you think is a game mechanic, but that in reality isn't in the game...hmmm.