To what extent is Dale Carnegie's philosophy and wisdom still applicable in today's world?

Answer 1

To the most extent I think it is applicable, but a slight changes are required which we can learn from our day to day life.
Most of the things have not changed regarding the peoples behavior or attitude so most are good to be applied in the present scenario.
I'm 32 years old and I learned most of the secrets from his book and apply in my day to day life and I see many do the same knowingly or unknowingly.

Answer 2

i think its very applicable
the concepts of "we cannot control all the situations that befall us, but we can at least control our attitudes toward them" and "that it is possible to change other people's behavior by changing one's reaction to them" are very usefull today as when he first spoke/or wrote about them
especially the "other peoples behavior", while that might not mean they change their attitudes, often we personally dont even have a need for that, though it would be nice, what we need it the behavior change, whether its a child, a coworker, anyone,