What you are talking about is Dennard scaling, which had transistors being able to go faster as they got smaller.

We still have Moore's law, which gives us more transistors. We just can't use them all at the same time and the individual transistors aren't getting faster (much).

For a while, we were able to use those extra transistors to wring out more performance out of sequential instruction streams by creating ever more complex out-of-order execution engines to figure out parallelism dynamically at run time. That also appears to have run its course.

Now we can use those extra transistors to add more cores, more cache and more specialised execution engines.