criticizing them.
I speak as a former leftie who even participated HEAVILY in the Occupy nonsense in 2011 and 2012.
The reason I could no longer stay with them and took a hard right is because, simply, anyone with the ability to form their OWN opinions via critique and critical thought of their own, just simply can't remain a leftist.
Just always remember, especially you lefties who might be lurking here in curiosity, "sounding" smart because you are repeating what you've been told is true, is not what intelligence is.
I have noted that and in poking hard (even without necessarily knowing the study or statistic or narrative), but just asking questions you often see how paper-thin the theory is. Something like "That does not sound right though?" "No, it absolutely is" "But wouldn't that mean...." The number of conversations where at that point whatever I said is simply not able to be countered by them at all. Then they get angry and defensive.
I will say it is not all people on the Left. The further Left though the less critical analysis you get. There are few Centre Left nowadays.