There are other disciplines that are important, as well. These include prayer, Bible study, meditation, fasting, etc. These are important. Not all of them need to be present to be healthy or growing spiritually, but each is important at various times in a Christian's life. I would say that being in regular fellowship, as opposed to "going to church," is important for spiritual growth. It's a slightly different nuance that certainly can include a weekly worship service, but there may be circumstances that prevent the weekly service attendance, and if you are still in regular fellowship with other believers, you can grow spiritually.