But they did? For Oblivion it was Gamebryo, for Skyrim it was the Creation Engine
https://en.m.wikipedia.org/wiki/Creation_Engine
The Creation Engine is a 3D video game engine created by Bethesda Game Studios based on the Gamebryo engine.
I mean that they haven’t changed it from the Creation engine. Which has been used since Skyrim despite some big rewrites for Fallout and I’m sure more big rewrites or additions for Starfield
But it’s only been 2 games since Skyrim, right? And for Starfield it’s being renamed Creation Engine 2. Either way that statement “Bethesda just doesn’t do that.” Doesn’t seem accurate when they have done that multiple times.