Odds of an adult being able to talk with the child in an informative way in a non-emergency situation and help them make a better decision for themselves: Extremely high.
You don't have to boss the kid around and treat them like a puppet you control to help them make better decisions.
Obviously (and it should go without saying, but I will say it anyway): Emergency situations are an exception. You can and should stop a child from sticking their hand in the fire without trying to nicely and at length talk them out of it while they are in the midst of doing so anyway.
You will also de facto be making a fair number of decisions on their behalf when they are below a certain age. Infants can cry to let you know something is wrong, but they can't tell you they need to be fed, etc. Adults have to do their best to figure out what the issue is and address it.
Good parents typically don't have a policy of "Oh, just let them cry it out." They typically feel that a crying child requires parental intervention to solve whatever their problem is.
(Exception: It's okay for them to just cry for emotional reasons. I never tried to convince my kids to stop crying about being told "no" or whatever. If you know they are crying because small kids have big feels, let them cry. No big deal.
But babies don't typically cry for emotional reasons. They cry because they have a problem that needs to be addressed.)
Odds of an adult knowing what's best for another adult: Low to Medium
Odds of an adult knowing what's best for a child: Medium to High