Uh, that's a bit off to be fair.

Our computers are 15x faster than they were about 15-20 years ago, sure...

But 1, the speed is noticeable and 2, not all the new performance is utilised 100%.

Sure, operating systems have started utilising the extra hardware to deliver the same 60-120fps base experience with some extra fancy (transparency with blur, for example, instead of regular transparency), but overall computer UX has plateaued a good decade and half ago.

The bottleneck is not the hardware or bad software but simply the idea of "why go faster when going this speed is fine, and we now don't need to use 15-30% of the hardware to do it but just 1-2%".

Oh and the other bottleneck is stupidity, like letting long running tasks onto the main/UI thread, fucking up the experience. Unfortunately, you can't help stupid.