One of the things which is appealing about Celtic spirituality is that it emerged out of a period when the institutional church had little influence. There is a sense in which it came out of an ecclesiastical vacuum. The emergence of British Christianity took place around the 4th century. It is likely that Christianity came to Britain by Roman soldiers who were sent into the region in the early 3rd century. In 410 AD Rome was sacked by invaders and its soldiers in the fringe areas were called back to protect the homeland. With the withdrawal of Rome, there came into existence a period of almost 200 years in which spirituality grew in Britain without any influence from Rome. This distinctive stream of spirituality flourished until the Synod of Whitby in 664 AD.
It has always been true that our beliefs have been shaped by the church. Not even today would any of us say that our spiritual life grew outside of the influence and teachings of the church. This is not to say that such an influence is a bad thing, but to say that sometimes the institutional church teaches us things which are experienced as contrary to what we know to be true in our hearts. Certainly, the medieval practice of buying indulgences is one of the more obvious. Over the years I have heard believers declare that baptism is a must for salvation and even go further to declare the necessity of being baptized in a particular church. Others have affirmed that being filled with the Spirit requires speaking in tongues. There are rules imposed about who can receive the Sacrament and who can offer it.
To say that our spirituality is not shaped to some degree by doctrines and disciplines of our church would be misleading. One of the interesting things about Celtic spirituality is the way it affirmed that we are created and marked by the essence of God instead of being marked by sin and iniquity. Whether we are ready to embrace a theology birthed before the 4th century church began to teach the doctrine of original sin is up to us, but it must be remembered that where we start has something to do with where we end up.