The engine is what allows the game to have a thriving modding community already.
Imagine relying on free labor to fix your broken ass game, and then having people defend you when called out for making a boring game that relies on free labor for content.
Imagine having that little understanding of how and why people enjoy modding their games.
Or what an engine is lol.
UE5 is “the same engine” iterated on in the same way Bethesda’s is, there are plenty of games using UE that don’t run well, and it would take plenty of custom work to build to Bethesda’s scale using it.
Imagine thinking that what is very probably the most hand-crafted content ever in a 3D game, with one of the broadest variety of choices for anything close to that scale, is a game lacking content.