It depends on how you define church. But if your definition of church is, or approximates the following, then I can’t see how you can honest conclude that an online church is really a church:
“The local church is a community of regeneration believers who confess Jesus Christ as Lord. In obedience to Scripture they organize under qualified leadership, gather regularly for preaching and worship, observe the biblical sacraments of baptism and Communion, are unified by the Spirit, are disciplined for holiness, and scatter to fulfill the Great Commission and the Great Commandment as missionaries to the world for God’s glory and their joy. (Doctrine: What Christians Should Believe, p. 307)
While, however, some of us cannot serious consider an online church really a church, we cannot ignore the need for an online presence, according to Ed Stetzer: “Every church should have an online presence, but a physical presence is necessary as well.”
For example, “When we take the Lord’s Supper together, pray for one another and confess our sins to one another, it is better done in physical community with online enhancement or augmentation, not replacement” (emphasis added).
“Ideally, churches will have an online presence, but will strongly encourage life-on-life interaction where social media enhances rather than excuses community. This can be one more tool that we have to introduce people to Jesus Christ and His church. It is not going away anytime soon, so we cannot just ignore it. Instead, we need to learn how to use it for God’s glory. If not, we will become increasingly irrelevant in a world shaped by the Internet.
Perhaps in certain extremities and physical restrictions an online presence is necessary. However, to quote Stetzer, “Your church should be online, but I don’t think it should be an online church” (read entire article).