I remember 20 years ago when performance really, really mattered, but now things are so fast it's a difference you can't always easily see

Yea, I remember back in the day a couple years old system would be obviously out of date and painful (IF you weren't just using it for simple stuff like office work) to use. The past 15 years or so things have been just so efficient and quick that I've been extending my hardware refresh cycles more and more.

I just replaced my old maxed out T440p with its 4th gen i7 last year after going strong since 2015