Because deacons have received the Sacrament of Holy Orders, they are among the ordained, not lay, ministers of the church. Because they do not receive the Sacrament of Holy Orders, religious brothers and sisters can be considered lay ministers. Some studies of lay ministers and of persons preparing for lay ministry create a separate category for religious brothers and sisters. Lay ministers can help meet the needs of the parish and the church, but there will always be a need for priests. As lay ministers collaborate more and more with priests, priests are freed to do what only they can.
Shortage is a relative term.
The United States has a much higher ratio of priests to Catholics than many other countries. In a recent document written to the Church in America, Pope John Paul II urged pastors to encourage lay leaders in the community. Lay ministers have long been assisting in the celebration of the Liturgy. They have been servers and musicians and choir members for centuries. Since Vatican II, lay ministers have participated by reading the Scripture, reading the general petitions, and serving as extraordinary ministers of communion.