The correct answer is "whenever you discovered there was an alternative". Windows has always been shit, but before you thought there was no alternative so you were used to it, ever since you started using something different you've grown less tolerant of problems. It's like someone who's always had a low end PC and played games on minimum at 30fps, it's "okay" but the moment you play something on maximum at 144fps your normal experience feels sluggish and bad (even though nothing really changed with it).
I think windows is the same thing, which is why most people will tell you the last good version of windows was the one they were using when they migrated over to Linux.