To be fair, the Yuan-Ti pureblood is the most human-looking type of Yuan-Ti and can arguably pass themselves as human as long as they are appropriately covered (so some of their features don't show, kind of like how undeads worked in DOS2). So narratively, it can be less disruptive than some other races - say a minotaur.
With that said, the Pureblood probably isn't the first additional race I'd throw in there though. There really isn't a connection for them in the story line so far, and mechanically they are notoriously an overtuned race compared to PHB races (outside of the Variant Human). Especially so in BG3 where way more enemies cast spells.
