The short answer is: single-core cpu performance is not going up much in the recent years. The core count is still increasing every year. That is why graphics cards still see a strong rise in total performance, their usual work load is inherently parallel.

For typical server tasks, like web serving, we can just run several processes. Unix is doing this for decades. But even web serving is often cpu bound, if your SQL query runs only on one cpu.

The obvious thing to make programs faster is, to utilize as many cpus as possible to perform the computations. There is no silver bullet, but the recent years brought quite some progress. Go makes it easy and cheap to spawn off goroutines, the channels and GC help to make this a reasonable concept. Functional programming languages are even a more obvious candidate for parallel execution, as they have no side effects.