There is a lot wrong with this demo.
Firstly, it's another case of a disengenuous "RTX OFF" exemple. Standard minecraft mas had a soft lighting mode with smooth transitions beteween light levels and voxel based AO for years now.
Standard minecraft has always had emissive blocks too, but in this demo, when in RTX OFF mode, caves are 100% dark (with a flat ambient term).
Also, I think this new lighting, while visually striking, is not servicing the gameplay. Besides the many moments where the player visually mistook mirrors for open space and other funny odities of this type, I think it misrepresents the underlying systemic lighting system that affects gameplay. I am not sure of this one entirely, but if I'm not mistaken, areas shadowed by the sun respond differently to sun recieving ones when you are planting and performing other actions. To not have to worry about the path the sun makes across the sky, the game simplifies the shadowing into perfectly vertical occlusion.
And it also is not "physically correct" in that this "sun shadow" depends on the distance from the occluder. It doesn't create the most visually interesting shadows, but it is an easy to understand ruleset for gameplay. These mods that create realistic long sun shadows that move across the landscape throughout the game ignore the actual gameplay.
Finally, the diffuse GI seems very subdued and flatish in this interation.
They have competent volumetric atmospheric scatering, mirror and rough soecular reflections and shadowed area lightsources, but the actual diffuse GI (which I think is the most important one in typical MC environments) is quite lacking.
It's no wonder they created a whole bunch of new colored emissive blocks for this demo, and also had to artificially gimp the representation of the "standard" graphics path. An actual organic scene as typically seen in minecraft does not actually show that much improvement.
From the perspective of game design, this is a great sin. They are changing a game to service an outside tech, instead of creating the tech to service the gameplay.