What has changed in a very large way is that the people writing the Constitution were all gentlemen with a well developed sense of ethics and morality. Those who were not Christian were mostly Deists. They assumed that the White Gentlemen land-owners who ran the Republic would always do the right thing for the Republic. Unfortunately, this is far from true now but it is nothing new. Communism was doomed because it assumes "Each according to his ability, and each according his need." But humans are lazy and greedy, and fully half of them are lower than average intelligence.

"the inference would be that there is not sufficient virtue among men for self government" is a direct quote from Madison, that reflects this attitude. Well, guess what? There IS not sufficient virtue among men to run a country depending on that virtue. Charity seems to be filled with charlatons who buy private jets instead of feeding the poor. We tried for personal virtue, and it failed miserably.

So a government has to educate children, pay police and firemen, build roads, etc. because otherwise we have to live in Trump's proverbial shethole country.