This is a very complex question, but of great importance today, as the Church seeks renewal.
This term, 'laity' ( referring to baptised Christians, as distinct from the ordained) only came into use at the end of the Patristic period (c. 100-450). It is misleading. The phrase, laos theou (People of God) is biblical; and in the discussions of Vatican II was used of the Church, as a corrective to the highly institutionalised self-understanding of the Church which had been taken for granted for centuries. 'People (laos) is the plural of person. As our review of historical developments will show, it is unfortunate that, after the council, this phrase has almost disappeared.
A far more appropriate term is 'the baptised'. St Augustine (d 430), more than once in speaking to his people declared, 'With you I am a Chrstian; for you I am a bishop'. Clearly, for him the blessing of Baptism was far more fundamental and important than being called to serve the community as an ordained bishop. It is Baptism that brings the Church into existence, and which established the fellowship which united Augustine to his people.
I have (in The Emmaus Series DVD, 'How is Church Ministry Changing') reviewed the historical developments in which what was taken for granted in the early centuries - a Church made up of small communities presided over by an ordained leadership without any distinctive dress - had to change. In the large communities which developed, in which a minimum of formation was taken for granted, all the functions in which the baptised had taken an active part were taken over by the ordained. By the end of the Middle Ages, the baptised had become little more than passive spectators in the Liturgical Actions which are the very life of the Church. And this situation continued until the 20th century. A dictionary of Catholic theology, published in Germany at the end of the 19th century, under the entry 'Laity' had 'See Clergy'!
The 'clericalism' which is one of the principal problems in the life of the Church today was the inevitable outcome of this situation. When a particular group in an organisation has taken over the essential functions in the life of the organisation, they develop a culture which sets them apart from rank and file members, and the collaborative life of the organisation suffers. In today's Church, those who have been formed in the centuries-old clerical culture find it difficult to adopt the collaborative leadership which can bring new life to our catholic tradition.
One of Jean-Claude Colin's preoccupations as the Founder of our Marist tradition was to guard against Marists adopting a clericalised form of ministry which he recognised was not appropriate in our changing world. The Marist Way he saw as an antidote to the shortcomings of the prevailing clerical culture.
Long-standing cultural traditions in large organisations are hard to change. We can take heart, however, from the fact that the best theology of the postVatican II Church is already point the way forward. The French Dominican, Yves Congar, made a unique contribution to the renewed self-understanding of the Church which found expression in the teaching of Vatican II. Writing some years after the Council ('My Pathfindings in the Theology of Laity and Ministry', in The Jurist (32  p.118) Congar declared that since the Council, his thought had undergone 'a Copernican revolution'. Some years before Vatican II, Congar wrote a much acclaimed work, Layi People in the Church. It was one of the first serious studies of the place of the baptised in the life of the Church. His approach in that book, he wrote, needed correction. In it his understanding of the origins of the Church was 'from the top down' - God brought the Church into existence through the gifts which were given to the hierarchy. This approach, he wrote, did not recognise the mutuality that exists between the gifts given to the baptised and the gifts given to the ordained. In his new perspective, he interpreted the origins of the institutional realities and the giftedness of the Church as realised through the Paschal Mystery of the Saviour.
He sumnarised his new understanding, stating that the Saviour has 'instituted a structured community which is' in its entirety 'holy, priestly, prophetic, missionary, apostolic; it has ministries at the heart of its life, some raised up freely by the Spirit, some by the laying on of hands linking them to the institutional ministry of the twelve'.