You are assuming a lot here, it’s a new tool and people are messing arround with it, doesn’t looks like a problem to me. If you don’t need assets with millions of polygons, just don’t do it. Nanite has better culling, better overdraw, better materials management and can handles way more instances that was previously possible, so it’s not just about the number of polygons. By the way Lumen is only possible because of Nanite, take that away and Lumen goes with it. Did you watch any of the videos Epic made on the new features? Because it doesn’t looks like it.
On the matter of size, yes you have more polygons, but you don’t need other stuff, like 4k normal maps that also consume memory. The compression system of Nanite already does a good job and is bound to improve, at this time having a million of polygon is not that expensive memory wise. Also considering that the project size is bigger that the release for the customer, one reason is because you not only need the Nanite version, but also the original raw data whitch is even bigger. In the Valley of the Ancient, Epic also said that most of the space is occupied by textures and it is a demo, unoptimized is many ways, just check the video for the explanation. The final released package is 20 GB not 100. Your 1 TB size for a normal game is completely made up.
When I said I wasn’t fully sold on the Lumen feature I meant on the technical side, the outcome is clearly something we all want and yes, it is a revolution, but the way they achieved it, I don’t know, it seems to have a lot of exceptions and limitations and goes in a different direction than the HW manufactures. I’m just a little bit more cautious to belive that this solution is generalized enough to scale into the future. I’m waiting to see what happens when they get a decent HW acceleration support and I wanna see how they handle high quality reflections.