I started improving after I took a free 10-day meditation course (the Goenka one), four years ago. At the course, I gained the ability to notice changes in my emotions and mental state. Suddenly, I could see when my mind switches to a judgmental attitude. I began intentionally trying to prevent the switch. I also intentionally restrain myself if I do switch into that mode. Changing mental habits is difficult and worthwhile. I have improved a lot in this area in 4 years.
Two years ago, I realized that my parents taught me to be a judgmental jerk. Since that time, I have considerably reduced the bad mental habit. People close to me confirm this. Therefore, my experience contradicts your statement.
Despite my half century and having repeatedly listened to and ruminated about "being judgemental", I can't fully fault "making judgements", for without judgement we have no comparison of worse vs better, and without that we have no basis for improvement. At issue mostly is _hasty_ judgement, uninformed, and without humility of all the potential and unknowable errors in judgement. But we definitely must judge, or stagnate.
Judging pointlessly is a big one, too. Especially if unhelpful levels of ill emotions are all wrapped up with judging things to be bad, which is so common I think it's fair to call that most people's default state, unless they've taken effort to change that.
Fixing those (forming judgements when they serve no purpose; feeling excessive ill emotions over judgements) is about half of the self-improvement part of stoicism, as in "think the right way, and act the right way". It's most of the "think the right way" half.
