But worshiping "in spirit and truth" and worship at Mass, at a Eucharistic liturgy,  are not mutually exclusive, especially for members of a liturgical church community (otherwise, join some non-liturgical church like the Baptist or Congregational churches). 

The purpose of Catholic liturgy, among other things, is to remind us how difficult it is to remain just one person in worship, especially when our church doors are open, and guests and regular worshippers can come in and out at will. 

We are also communitarian worshippers at heart (in the broader sense), whether in church or in our neighborhoods. Mass simply reconnects us liturgically to Christ -- in a unique way, sacramentally -- to serve Him better in our neighbor. 

(The young people and older in parishes in CA, FL and New England with which I am familiar understand this only too well.)