[torginus]

There are tons of examples of physics engines running on the GPU. Contact resolution (particularly between simple shapes) is an embarassingly parallel problem. I don't think it would be impossible to handle millions of collisions per frame on a modern GPU, maybe even CPU. Also, what counted as a high-end server a decade ago probably is much more affordable with today's technology. You can also probably design a scripting system/set of game rules which allow unobserved NPCs/objects to sleep when no player is around them.

User content can probably be limited as well so that people don't upload overly complex/poorly performing 3d assets.

I'm not saying that this isn't a tall order, but I think it's far more manageable by a sufficiently determined and talented team than it was decades ago.

[thu2111]

Sure, technology makes some things easier with time. But the needs for content to be optimized has not really gone away, and the issue was not necessarily overly complex 3D assets but that the very structure of what people wanted to build was difficult to optimize for. Many AAA games are set in indoor areas with no windows, because this limits how much you have to draw. In second life, almost everywhere the camera could see long distances either because you are outside or because you're inside in a room with windows. And that doesn't seem to have a really easy technological solution, although maybe Unreal's new nanite can do something about it by avoiding the need for custom LOD meshes.