This is not true. I thought the same thing and you are right in regards to base line clock speed. But the performance is still increasing. I just got a new PC at work with a 2021 high-end CPU and it has 200% single core performance of the 2015 mid-range CPU in my private PC:
https://www.cpubenchmark.net/compare/4597vs2599/Intel-i9-129...
Also, the comment you're quoting is talking about clock speed, and the link you provided literally shows the same base clock speed - 3.2 GHz. Intel progressively pushed turbo speed higher, but that the speed you could have achieved yourself by overclocking.
On my water cooled and specifically tweaked desktop- yes. It’ll hold max boost indefinitely, even with all threads. (getting to about 80c after 10 mins). Single-thread max is faster, and it’ll hold that as well.
My laptop will pull power within 15 seconds and be down to base clocks in a couple mins. Unless I set it down outside and it’s very cold.
Other things changed. The turbo clockspeed is one of them.