I think you´re referring to how goblins are depicted in past editions. That is not the case anymore. You find goblin villages and a goblin merchant in several adventure sets of the FR setting or even in Chult. And yeah, all goblins speak goblin and common.
That seems to be the case, I'm too used to the older editions. I guess it's time to stop being a troglodyte and adapting :'D
