The church is designed as the body of Christ. The sanctuary on Sunday morning is specifically a place for the people of God to come together for corporate worship, for the study of the Apostolic Word, and to make use of the sacraments and the other means of grace.
Of course, unbelievers are welcome to attend. But the minute you design worship for the unbeliever, you’ve missed the whole point of biblical worship. That’s a very dangerous tendency we’re seeing today.