Compare the AMD Ryzen 7 9800X3D to the AMD A12-9800, you go from 4 cores to 8, and you double the power consumption. But it's not twice as fast. It's 10 times faster. Depending on the exact metric, it could be as little as twice as fast or as much as 1000 times faster, depending on the exact operations.
On top of that memory throughput between DDR4 and DDR6 is about 2.5 times faster as well.
Oh and this isn't 20 years apart, this is 7 years apart. 20 years will see almost an exponentially larger gap even still.
AI datacenters, absolutely. People? Nah we probably use 10 percent for 90 percent of the time.
But when I need to compile MAME, oh boy is it nice having a fast CPU.
If we're talking about video game graphics it's a bit of a mixed bag.
If we're talking about local LLM models then you need all the power you can get.
Etc, etc.
I don't think I had any in my builds until 2014ish
These days, I feel the most performance uplift when I switch from Windows/macOS over to a Linux or BSD installation, if only because there is so little wasted effort in running a bajillion little background tasks for crap I didn't ask for. Windows 10 on my PC is highly debloated and optimized, very little in my startup services and so on, but CachyOS on the same hardware feels leagues better.
Its not Linux, but all hardware worked on Windows XP. Nerds were familiar with tweaking the registry, doing all kinds of hacks and helping all their friends and family. Of course, cleaning out the thousands of viruses from friends computers wasn't fun ..
Then Microsoft released Windows Vista, yuck!
When the M1 was released, I couldn't believe how fast it was.