On CPU Benchmark the i7-2600K scores an 8449 [1], while the i7-8700K scores a 15970 [2]. The i7-8700K is the predecessor to the i7-9700K reviewed in the article.
[1] https://www.cpubenchmark.net/cpu.php?cpu=Intel+Core+i7-2600K...
[2] https://www.cpubenchmark.net/cpu.php?cpu=Intel+Core+i7-8700K...
The score you gave is the multi threaded benchmark that is just higher for having 6 cores rather than 4, that regular applications don't use.
Newer intel CPUs turbo higher at stock (you could say that OC is sort of built in) so single threaded performance looks better than it really is.
Now 32nm at 4.8Ghz would be quite power hungry but that is not the issue here.
Pretty much all the progress Intel has achieved in the last 7 years since Sandy Bridge has been in achieving the same performance for less wattage focusing on mobile use cases.
(on server side Xeons have increased the core count substantially but again single threaded performance IPC has stagnated)
Thus mobile i5-8250U gets to claim that it does about the same in 15W that 2600k did at 95W.
Remember we are still on the same Skylake Arch from 3-4 years ago, just a few minor process tweaks on 14++++nm plus obviously 2x the number of cores.
If you're playing games, you'll get better performance with this i9.
But if you're playing games, you're probably not CPU-bound anyway.
I'd be interested in what niches people here work in and what CPUs they look for because of their unique needs.
We used to say this, but I don't believe it anymore. A lot of games these days make heavy use of simulation and physics engines. Games like KSP that perform continuous physics calculations are absolutely CPU-bound.