How could it possibly be otherwise? Single core performance goes up every year, but not enough that this year’s 12-core CPU beats last year’s 18-core CPU at multithreaded benchmarks.

This is “sad”?!? First world problems.

It's also not exclusive to Apple; the normal product cadence from Intel and AMD usually has the large workstation and server chips falling behind the consumer chips in peak single-core performance for part of the product cycle. Some market segments just don't sustain annual updates very well, and it's always easier to get a smaller chip out the door first before a larger chip.