The proverbial “wall of separation” is a good thing… at least as it was described by Thomas Jefferson to the Danbury Baptists.
While most of the “christian” religions (Catholics, Reformed, etc) wanted a formal state enforced religion, the Baptists (and a handful of others) were well familiar with what being on the wrong side of a state enforced religion was like…
When we look through the un-doctored history of the church we see a pattern of true believers being persecuted and martyred by state enforced religions. Christians were persecuted by the pagan Roman Empire, then by the Catholic Roman Empire, then by the monarchy and oligarchy governments that enforced Roman Catholic, Orthodox Catholic, and/or Reformed Catholic (Protestant) traditions by burning or beheading anyone that dared question them.
The persecution of the Anabaptists was still in recent memory of the Baptists, and was one of the driving forces behind them coming to America, not to establish a new state religion, but to have an assurance of being free to practice their beliefs without interference by the government.
The wall of separation was to be a “one way” wall, to keep the government from interfering with the practice of religion. They felt that government was a bad influence on the practice of religion. However, it was clear that the founders felt that religion could be a good influence on the practice of government.
Religious beliefs are yet another set of checks and balances to keep the government contained and in line. Religion works best when it is at odds with the government, not in cahoots with it.
The role of government was to protect religious freedom (thought, belief, and practice), but should never be used to enforce a religious system or otherwise interfere with any other religions.