It's Very Difficult for Bethesda Studios to Replace Creation Engine with Unreal Engine 5
Former lead designer of Skyrim, Bruce Nesmith, commented on the opinion that Bethesda should switch from Creation Engine to Unreal Engine to speed up development. He called this opinion mistaken.
Creation Engine is not just a graphics tool; it's the foundation of the entire architecture of the studio's games. It contains the data, logic, and interaction of all systems, as well as development tools. Simply "turning off" one engine and "turning on" another is impossible.
Such a transition would not speed up the process; on the contrary, it would require enormous resources to recreate Bethesda's unique systems from scratch.