why do you think rangers and fighters shouldn't have been getting a flanking benefit?
I have mixed feeling with flanking:
5e's flanking turns into everyone has advantage, and that's boring. The risk of combat goes away, and initiative order settles combat outcomes.
Flanking providing +2 to hit is alright, but can still have a domino effect.
Also with how many encounters the party is outnumbered in BG3, flanking would work against the player more often than for the player.
Cover or a homebrewed "flanked" would be more appropriate for BG3. Flanked being something like... if the character has an enemies on two or more sides -1 AC and 1/2 movement.
