Death by a thousand cuts.
Yes, things like small bugs and abnormal user experiences accumulate and over time the OS and other apps become inconsistent.
As heavy users who are generally by profession spend a lot more time with a Mac, they tend to experience more issues, and things that used to work for decades start to crumble. It all works if you’re acting like working on glass pieces, but that’s not what computers are made for.
You’re supposed to use it extensively and get more efficient over time without a glassy UI and other broken systems pulling you down at every turn.
It’s not about using a system for 10 minutes to visit a website with Chrome, but instead spending days programming things, having a normal life, and still having the very simple file discovery features working.
There’s no reason for a computer to be this choppy and slow (in things like context switching etc.) unless something else is going on in the background.