We've been moving sideways for 10 years. In the 20 years before that, clock speeds were doubling every year or two. For the last 10, we've moved from a norm of single cores to a norm of 4 (or 2 + "Hyperthreads"), rotating hard drives to SSD, and specialized architectures to support HD video, but clock speed has been basically stagnant while the processors are getting fatter, more parallel, and not just in core count.
We hit a wall on MOSFET clock speeds way before we expected. Turns out that power consumption is quadratic, not linear, to clock speed. Once you get over 4GHz or so, it becomes a substantial problem, and getting over 5GHz is a real ordeal. There are ideas for non-FET transistors, but so far none has worked out.
10 years ago, Intel was hinting at a massively parallel future (80 core processor rumored in development at the time), they've been slow to deliver on that in terms of core count, but are making progress on other fronts - especially helping single cores perform faster without a faster clock.
Well, Intel was right. They just aren't CPUs, but GPUs. Even a bottom-end GPU will have 80 cores, the price/performance is pretty good all the way up to 1500 cores, and if you really want, you can get 4000-core cards. Those "cores" mean "ALUs", but even if you demand your cores have discrete schedulers, an R9 Fury has 64 compute units (scheduler + 64 ALUs), so 64 separate threads at once, each of which has massive SIMD power.