It's taken 20 years to go from 250nm process to 7/10 nm process, most of the biggest changes happening in the first 10 years or so. Back in the days of FX, amd split from convention thinking and expanded core count vrs Intel which has concentrated on single thread performance. If the nm process allowed, we'd still be looking at Intel quad cores for mainstream, but the nm process won't allow it. Simply can't (yet) get 7nm to 5+GHz speeds. Intel could easily drop a 7 or 10nm desktop cpu, but would be restricted as amd to closer to 4GHz and that would be bad for Intel as software still is oriented on single thread speeds.
So it's going to get to the point (5nm) where silicon based ic's aren't going to be enough. A brick wall. That's what's coming. There's going to be only 1 direction current ability can go. Out. Multi cores, multi threads, and with games like BF4 and up, it's already started. 2 threads at 4GHz get more work done than 1 core at 5GHz. Ask any slow Xeon with 18 cores at 2.x.
So that's where games and other software is headed for the foreseeable future. Higher thread utilization. The I5-9600k is good for now, but going to get increasingly, proportionately slower as games get optimized for 8, 12, 16 thread usage.
This puts the higher thread count amd mainstream cpus at an advantage. They may not get the highest fps, that honestly doesn't matter, it's the spread between highest and lowest fps where amd is the winner mostly, having the lower variation.
But that could also be 10 years from now. The mistake amd made in jumping the gun with high thread FX and no supporting software to speak of.
So either take full advantage of DX11 games and higher single thread now, or gamble on the need for higher multi-thread.