I don't think it needs mentioning. It is impossibly hard to keep the same culture at a game company two decades later, especially when the company grows so much. It's not like Valve is the same Valve that released Half-Life, or Bungie is the same Bungie that released Oni. None of these companies today could possibly have a similar culture to what their company culture was when those games came out.
Changing company culture, it turns out, is easy. Stupidly easy. I say it's "stupidly" easy because all you need to do is hire new people, and most companies already do that. The hard thing is changing company culture in the right direction.