what do you mean by "pretending that voltage numbers and current numbers cancel out in certain ways"? The problem is certainly not that our mathematical models

what do you mean by "pretending that voltage numbers and current numbers cancel out in certain ways"? The problem is certainly not that our mathematical models are insufficient. Transistor I-V characteristics have been quite complicated for several generations now. That's why circuit designers use computer simulations now, not hand-cranked calculus models. The slow-down in processor speed despite shrinking transistor is due to physical and design limitations. For one, it used to be that you could use more transistors to build more complex pipelines, branch predictors, etc. to allow you to turn up the clock frequency. But now we've reached the point of diminishing returns on this sort of optimization. Also, increasing the frequency increases the power, which causes problems for heat dissipation and chip lifetime. So we've cut back on frequency to lower the power consumption.