With past mainline versions of Unreal Engine, Epic would usually kick things off with a flashy tech demo that pushes photorealism to a new level. That didn't happen with Unreal Engine 6. Because while the company showed off the same Rocket League UE6 teaser that it did a couple weeks ago, Epic CEO Tim Sweeney spent way more time focusing on his vision of an open games ecosystem. The idea, on the surface, is to get rid of the barriers…