From Will Durant's The Age of Faith:

[T]he Church became the largest landholder in Europe, the greatest of feudal suzerains. The monastery of Fulda owned 15,000 small villas, that of St. Gall had 2000 serfs; Alcuin at Tours was lord of 20,000 serfs....Bishops or abbots accoutered with armor and lance became a frequent sight in Germany and France; Richard of Cornwall, in 1257, mourned that England had no such "warlike and mettlesome bishops." So enmeshed in the feudal web, the Church found herself a political, economic, and military, as well as religious, institution...

and, regarding slaves:

Pope Gregory I freed two of his slaves with admirable words about the natural liberty of all men, but he continued to use hundreds of slaves on the papal estates and approved laws forbidding slaves to become clerics or marry free Christians...Canon law sometimes estimated the wealth of church lands in slaves rather than in money; like secular law, it considered the slave as a chattel...The rule of the Church, that her property should never be alienated except at its full market value, was unfortunate for her slaves and serfs; emancipation sometimes proved more difficult on ecclesiastical than on secular properties.

These are just two of uncountable examples of the Church usurping secular responsibilities for herself. All of it is unconscionable and should never be suffered of any religious institution.

A church's roles should only be-

1) Keeper of the information about what they believe

2) Performer of the church's sacraments/rituals

3) Services, but only if the church chooses to be about that and only through the resources it or its members can rally.

Basically a church should be there to facilitate life and advise and inform people who choose to participate. Although that advice might extend to other areas like politics a church should not drive in those other aspects of society at least in nations with civil rights including freedom of religion because any church with formal political power risks stepping on other religions or the nonreligious.

A church (or religious whatever), should live by their own morals (within their cult), and leave society to make the morals OUTSIDE of said cult.