Definitely not! We advocate using the practices and techniques we explore at MMC as one tool of many in your efforts to bring the people you worship with, live among and work alongside together through liturgy and music. We would never advocate that you try to lead a Bach cantata without written music (though if you did, we would most certainly want to hear about it!), and wholeheartedly acknowledge that written music is a valuable part of worship and life in general.
On the other hand, we've found that singing some songs without books or screens can invite a more relational experience. We think singing this way emphasizes listening and awareness, and can give the stranger a way in to music making, and therefore, to community, in a way that can be hard to accomplish with written music that requires special knowledge to interpret.