It was votes of the young, naively optimistic/self-interested (abolition of tuition fees), or the old, cynical/self-interested baby boomers, who betrayed the nation. Or at least, that seems to be the underlying theme of election commentators.
What is wrong with self-interest? If the working class of any age was more self-interested it wouldn’t continue to put up with the fundamental cause of its problems, capitalism.
The young, the old and all in-between have a common self-interest in creating a society that meets the needs of them all, not just the profit of the very few.