At this point, we should just be looking at IPC improvements at the same frequency/voltage and power consumption to see if there are any improvements.
And yes, sure, more cores are nice, but tons of useful software is still bottlenecked by single core speed. So is general computer responsiveness.
I refuse to believe at current high end intel/amd levels (i7-9 & ryzen 7-9) & even mid-range that lack of responsiveness is due to the CPU rather than windows/mac.
You are right, of course, in that the fault lies with software. But holding the software as constant, the only way to improve responsiveness is to up your core speed and IPC.
It's not as if the average user can email Microsoft of the Chrome browser team and ask them to make the OS/Browser more responsive for their older hardware. But they _can_ go to the store and buy a faster CPU, most of the time.
The situation was probably reversed a few decades ago, when hardware was actually expensive and multi-core was not a thing.
[0] - I’m talking about Office 365 which runs in a web browser (yet somehow is no slower than the “native” version that runs on my desktop computer).
Again the "poster boy" for responsive interaction is probably BeOS - the original BeBox used dual ppc 603 CPUs at 66mhz: if you consider IPC, Mhz & number of cores a modern CPU probably has 1000x the computation power at its disposal & RAM is also generally 1000x more plentiful (we have as many GBs as we used to have MBs back then). I'll bet with GPUs the difference is even bigger.
Typical RAM module (DDR-266) in late 90s could only provide ~2.1GB/s, leaving almost no room to perform any compute on a single 4k screen, and simply insufficient to run two of them.
PC66 of early 90s could only do 0.5GB/s.
DDR3, commonly used now in integrated GPUs does 13GB/s.
What I am getting at, is that the task to just copy pixels to a screen became proportionally harder as RAM progressed forward (26x faster per module since 1990, 6.5x per module since 1999 vs 60x more work per screen since 1990 (256 colors), 10x per screen since 1999).
And that is just screen rendering. Same happened to source code, documents, images, everything.
It's interesting to see approaches like Apple's where more and more of computationally heavy work is moved onto what are essentially special purpose purpose ASICs (I think you can generously expand the definition to even include GPUs). Specific examples include video decoding, graphics, and increasingly ML computation. Once those things become "free" what is left? I'd say mostly just many layers of abstractions atop basic computation.
As more and more software stacks become ergonomic w.r.t. multithreading & multiple execution contexts, single core becomes less of a bottleneck. IMO that's the ultimate solution to the hard physical constraints of Moore's Law. Short of a new type of compute substrate.