Earlier quoted context omitted.
There is a very real difference between constructive criticism and simply complaining. In most cases, complaining and shutting people down without suggesting any possible alternative or improvement just makes the situation even less unpleasant for everyone.
Sometimes complaining means acknowledging that a problem exists even if you don't know the solution. Pointing out problems is valuable too. On the other and the people[1] who "opt out of cynicism" generally want to live in the "best of the possible world" where problems just disappear if don't look at them. [1] that I've met and interacted with, of course there's a sampling bias.
Pointing out every problem, all the time, isn't.
It's a very fine line and not everyone manages to stay on the right side.