What is Steinbeck saying about loneliness and isolation in Of Mice and Men?

's novella
speaks directly to both isolation and loneliness.

Curley's wife, who remains unnamed, feels both isolated and lonely. She is the only
woman on the ranch, and the men constantly remind her that she is unwanted. She, essentially, is
isolated because of her gender. Given this isolation, she feels no sympathy from any of the
other people at the ranch. Therefore, her loneliness is obvious. She has no one to talk to or
who relates to her.

Candy is another character who feels isolated and lonely.
As one of the older men on the ranch, the younger men do not seem to see his worth any longer.
His only "friend" is his beloved dog. Unfortunately for him, Carlson complains so much
about the aging dog that Candy allows Carlson to put the dog down. At this moment, Candy feels
as though he has lost his only friend. Because of his age, Candy feels both isolated and
lonely.

In the end, Steinbeck is stating that most people, at some point in
their lives, will feel...