Gamebryo was called netimmerse until 2003. Creation is a modified gamebryo. So Creation 2 will also be based on it. So yes they use kinda the same engine since morrowind. Beteshda will not change away from it because gamebryo is a large reason why the modding community is as strong as it is for skyrim etc. And the modding community sells a lot of copies!
The engine also started as an engine for MMOs, which allowed them rich scripting for every NPC, as well as an inventory for every NPC.
The world fidelity that Bethesda builds, on a technical and simulation level, is unmatched — yeah, something like The Witcher 3 might look better, but it also doesn’t let you interact with basically every item in the world or pickpocket every NPC’s weapon as a way to neutralize them in combat.
