Universalism which basically says that religion is a universal construct to explain our daily world is a new name put onto many ideas in the past. There have not always been the main 3-5 religions that we have now. Many people in the past have thought similar ideas, just with different names.
Many religions share similarities in their philosophies and expressed set of values. To this degree, it is very easy to find commonalities across multiple religions. Universalism, in particular, is basically just an encapsulation of this theory. Despite their similarities, however, there is no evidence to suggest that all religion can be traced to the same root or that religion is inherent to humans.
Universalism is not another new form of an ancient religion. Universalism teaches that all religions are correct and that each individual is heading for the same destination. So rather you're a follower of Christ or you prefer Islam, you're headed to the same general place, you're just taking different paths. Universalism tries to keep the golden rule at the center of its teachings. Its not an ancient religion, its more of a different perception of the religions we already have.
While universalism still has religious roots, universilist still believe in religion, it is not a new form of ancient religion. Ancient religion specifically believes in their religion and only their religion where as universalism allows people to believe in their own religion but not judge others or shun others if their beliefs are different.
Universalism is an idea that tries to bring all of the religions together, not to give up their beliefs, but just to realize that we are all headed to same place or have a common goal. Universalism is a theory that tries to right what is wrong with religion or what becomes a problem when parishioners of different religions go against each other.