It is not only that. I remember reading some article where someone did actual measurements. Some of the delays are attributed to just how for example keyboards

It is not only that. I remember reading some article where someone did actual measurements. Some of the delays are attributed to just how for example keyboards as such work like amount of movement needed before an electrical keypress signal happens and stuff like that, plus the whole processing chain following. And that is where these older computers are much much faster, because USB or worse, Bluetooth, only allow for so much low latency. Plus there are insane amounts of signal processing steps before it even arrives as an interrupt in the CPU, let alone is processed into some actual OS input event, and then it still needs to go through various levels of application software layers. And that is just the input side, the whole thing has to lead to screen updates and this is another level of technocraziness.