I have probably walked out of 7 - 8 shows in my life (almost 60 years). I am not sure I ever waited for intermission for most. In the late 60s, I walked out of How to Be a Jewish Mother in its Boston during the first act. It was agony and I was on the aisle in cheap seats, so no one was disturbed. 50+ years ago I walked out on Jimmy, one of the worst shows I ever saw, at intermission, preferring to walk around waiting for the three people I was with, rather than sit through it another minute. They all agreed after the show that I made the right decision.
Since that time, if I really really hated a show, e.g., Dr. Jazz, Onward Victoria, Ulysses in Nighttown (well reviewed, but I hated it), a Pinter play whose name I do not even remember, and a few others. I have always made a point of getting an aisle seat whenever I could, and many of them were also in the cheap seat zone, so no one on stage was going to be distracted.
nowadays, I generally think there are fewer real stinkers than there used to be, and my wife doesnt like to leave, so I have daydreamed through more than a few bad (to me) shows. We’re I alone, if I was bored still, I would still leave. I paid for the ticket and am investing my time; I feel that gives me the right to leave…to the best of my knowledge, the last time I left during the show was Rock of Ages, but I waited for intermission.