I was chatting recently with a young friend about whether it is possible to be spiritual without being religious. Put another way, is it possible to believe in Jesus without believing in His Church? I took the position that it is not. But I recognized that a growing cohort, especially among the young, take the contrary position.
Now, as it happens, I am currently reading Evangelical Exodus: Evangelical Seminarians and Their Paths to Rome, which is a collection of essays by young (mostly) Evangelicals who made/are making the same transition I made almost 20 years ago from being an Evangelical to being a Catholic.
One of the essays spoke to the precise problem my friend and I had been discussing:
The Catholic Church articulates the exact opposite—the remedy for individualism. The purpose of coming together is as follows: “It is in the Church, in communion with the baptized, that the Christian fulfills his vocation.” The Catechism provides the reasons for maintaining solidarity with the Church:
From the Church he receives  the Word of God containing the teachings of the “law of Christ” [Gal 6:2]. From the Church he receives  the grace of the sacraments that sustains him on the “way.” From the Church he learns  the example of holiness and recognizes its model and source in the all-holy Virgin Mary; he discerns it in the authentic witness of those who live it; he discovers it in the spiritual direction and long history of the saints who have gone before him and whom the liturgy celebrates in the rhythms of the sanctoral cycle [that is, the feast days, or propers, of the saints].
Beaumont, Douglas (2016-02-11). Evangelical Exodus: Evangelical Seminarians and Their Paths to Rome (Kindle Locations 913-920). Ignatius Press. Kindle Edition.
In other words, the Church provides a community within which one finds support from those making the same spiritual journey as oneself. It provides tools that encourage and empower one on that journey. Lastly, Jesus himself directed us to seek communal--rather than individual--worship: "where two or three are gathered together in my name, there am I in the midst of them.” Matthew 18:20.
So I agree with David Mills:
Being “spiritual” does not do us any good. As I recently wrote elsewhere, it works fairly well when you are healthy and have enough money to enjoy life, and just want from your spirituality the feeling that all is well with the universe, particularly your corner of it. But it doesn’t help you much when things go from good to bad.
The man wasting away from pancreatic cancer will get no help nor comfort from the “spiritual,” which will seem a lot less friendly and comforting when he feels pain morphine won’t suppress. He has no one to beg for help, no one to ask for comfort, no one to be with him, no one to meet when he crosses from this world to the next. He wants what religion promises.