It's hard to generalize. Common microcontroller clock speeds range from 1 to 500 MHz. An 8-bit microcontroller running at 1 MHz will often work fine without any

It's hard to generalize. Common microcontroller clock speeds range from 1 to 500 MHz. An 8-bit microcontroller running at 1 MHz will often work fine without any decoupling at all. A 32-bit microcontroller might not even boot without a ceramic capacitor nearby. The basic answer is basically what the original article says. If you don't want the mental burden of figuring it out, the spec gives you safe defaults that should work for almost all uses. But it's almost never the case that you need to do it that way.