In the sentence:
"Young people today have no influence on the important decisions that determine the future of society as a whole."
what does it mean by "as a whole"? Does it mean unanimity?
I would say that the phrase as a whole in this case has a meaning similar to that of the expression in the grand scheme of things (in the complete picture of something). Young people, of course, can and do have some influence on the things that determine the future of our society. The only difference is that that influence is small and local in scope and as a whole will not have a major effect on the way society is going to look in the not too distant future.