I was telling my wife about this poll and asked her what she thought would be the number one response. (Keep in mind she basically entered the hobby with 5e and doesn't frequent game sites like this.)
"4e - duh."
There are people out there who don't know they're "supposed to hate" this system, largely because it tried to do something new and innovative.
I have a real fondness for it. It was the system that I never really got to finish my ideas with. I never got burned out of it.
Just for me...
In the case of 3.x/PF1 - I would rather not play than ever touch that stuff again. I am so sick of it - adding up micro-bonuses, measuring hypotenuses, tracking dozens of spell effects and magic item bonuses, grappling. I DMed it and wrote for the system for around a decade - and I still never want to look at it again.
The TSR-era game is frustratingly impossible (RAW), with characters so fantastically weak that they can't even be heroes.