That's not really true of the first two things I mentioned. These required significant evolution in the DSP/math involved. In 1990, timestretching existed, but generally created artifacts. Polyphonic note editing (as implemented first by Melodyne) didn't exist and wasn't really even imagined.
It is true that they both benefit from more powerful hardware, but these examples required significant advances in software too.
It is true that they both benefit from more powerful hardware, but these examples required significant advances in software too.