Not necessarily subjective. When I go to the same places with the same noises, I used to didn't even hear the engines, machines, and music, now I distinctly hear them. I took off the AirPods and the noises were not louder than before.
But we can both be right, since the same software sometimes have different effects. Perhaps there are other variables. Just like how Apple bricks some iPads and HomePods just this month, but not all of them. There is already another thread on MR saying the ANC got worse.
I certainly wasn't looking for the ANC to get worse. In fact, I was surprised by it and checked several times if I had the correct mode on. Just like the other guy likely wasn't looking for it to get better either.