Okay clarification:
Are goblins vermin or fully sapient beings? Because some people on this forum talk about goblins like they’re innately evil rodents, and others talk about them like they’re people.
So the Key is that 5e did away with Innate evil for non-outsiders. They replaced it with Cultural Evil.
The Githyanki are Culturally lawful evil. Goblins are Culturally Neutral Evil.
As long as Goblins and Githyanki remain in their societies they will likely remain those cultural alignments. If they leave then those alignments can shift. A Goblin living in baldur's gate will likely be more Neutral than evil, or they at least understand what is expected of them. A Githyanki away from thier Creche or Society will start to drift as well.
Innate evil is Demons, Devils, Yugoloths. They CANNOT change alignment without becoming something different entirely. They are literally made of their versions of evil.
When Zariel fell and became lawful Evil her type changed from Celestial to Fiend and she is now considered a Devil.
