These are kinds of generic recommendations you listed are precisely the type that go out-of-date. Even on a laptop, I now have 16 threads and almost never see

These are kinds of generic recommendations you listed are precisely the type that go out-of-date. Even on a laptop, I now have 16 threads and almost never see more than 1 utilised even when I'm waiting. Any time a human waits for a computer that is just 6% utilised, a developer screwed up. Just this minute, I downloaded a program installer using a 10 Gbps Internet link. Yes. Ten gigabits, dedicated to me, personally! Your idea of "what is a fast Internet link" is wrong. I downloaded a 600 MB software package in less than a second, and then had to wait for 30 seconds while the anti-malware tools scanned it... with a single thread. Extracting the file was 10 seconds because 'zip' is by default single threaded. Installing it took a solid minute during which my CPU usage never peaked above 2 cores because the installer is also single threaded. The only reason it uses more than 1 core is because the anti-malware scans it... again... on a second thread. Similarly, any time I see anyone manipulating ~1 GB of data, invariably they do it with GUI or CLI tools that are single threaded. This was desirable in an era when everyone had a single mechanical HHD. Multiple read or write threads would have caused disk head seeks, slowing down the process. These days when everyone has NVMe SSDs, the only way to fully utilise the 500K IOPS available from a $150 device is by throwing dozens of parallel threads at it!