I was there for most of the old machines and my recollection is they were always slow, which is why there was a relentless race to upgrade to a faster machine and why for a very long time people replaced their computer once a year. If software and old machines were so snappy then there would have been no reason to buy a new computer, and the industry would have stalled in 1984.
This trope of "how did things get so slow, they were fast in ye olde dayes" is just an incorrect blurred memory of they way things were.
AND if the software was faster in Ye Olde Dayes, it is because it did less.
Of course it's not possible to generalise, but for the most part this is true - old software did less than modern software. The pervasive experience of using old computers was waiting.
My M1 Mac running 2 IDEs, 3 web browsers, email, terminals and several other apps is ridiculously, mind blowingly, insanely fast - so fast that anyone back in 1990 would have drooled themselves dry to have that speed.