There’s lots of surfaces reflecting direct lights, not geometry. It’s somewhat similar to setting the glossy reflections to zero in Cycles. Yes, reflections are easy with pathtracing, which doesn’t necessarily imply they’re cheap when you make them rough and cover your whole scene in them. They cost precious rays that could otherwise be doing diffuse bounces.
My point is not that the renderer is rubbish, in fact it’s probably quite nice. It’s just that the author used his intimate knowledge of pathtracing to choose a very convenient scene and optimized the shaders and lighting very well. Which would be admirable if he was an artist. But since he’s trying to sell us on his engine, optimizing his scene that well is not very convincing.
But I’m not going to try to convince you, believe what you will. Again, it’s not that Arauna 2 is bad, it’s that Cycles is probably very close.