I personally like it, because it adds a tactical aspect to the game, that I feel flanking doesn't add.
I get peoples frustrations with it though. I don't find it too tedious, and makes playing a melee fighter at least somewhat more interesting than "point, click, miss"
Flanking would mean you have to keep two melee characters on the one opponent at all times... not sure I personally would find that more fun to be honest, especially since the battle maps are very big and dynamic.
In my DM games we use neither system, we instead allow for the players to use the "help" action as a reaction to confer advantage. It's to simulate flanking and distractions.
(Of course the help action is completely different in BG3)
As for the "only sneaking characters should get it" argument, Rogues already get Sneak Attack, which works off of advantage, they don't need to sneak to get it though.
