> at current computer sizes
This. No, not at all at current computer sizes, but at future computer sizes. This is the same mistake someone in the 1970's might make about billions having a smartphone today (supercomputer by their standards). Consider how everything at current computer sizes is effectively two dimensional, even stacked processors are still fundamentally 2D designs. There is still a lot of computing advancement ahead. 40 years from now they'll look back and think the same things we think when we look back 40 years, that the machines were so primitive, hardly anything could be done with them, and some will be nostalgic for them, talk about their strengths, while others will shake their heads and think even messing with the fastest workstation today is a waste of time. Just because we can't conceive of how, doesn't mean it's not possible, some day.