I don't think we've seen the last of the Luminous Engine. Although XVI utilized Unreal in its earlier stages, many people seem to think the final product will utilize Luminous. I doubt SE would let it go to waste. As far Crystal Dynamics goes, their history of mistakes is as old as the company itself. I'm sure they fully intended to push The Message™️ with the Avengers game. I'll give SE the benefit of the doubt and assume they just wanted to capitalize on the popularity of the Avengers franchise at the time. That's why they were looking for another sucker to offload CD to after the game flopped.