I think it would be most accurate to say that Reformed theology has always had great resources within it for missional work. For example:
- Stanley Grenz credits Calvin for teaching on the Trinity that stresses the communal aspect of God’s nature,
- Richard Muller points out that Post-reformation Calvinist theologians forged a theology that wasn’t ‘modern’ and based on traditional rationalistic proofs of God,
- Jonathan Edwards provides theological resources for profoundly mystical personal experience of God,
- Geerhardus Vos and Herman Ridderbos stress that the Bible isn’t a systematic theology textbook but rather a narrative of creation, fall, redemption, and restoration,
- Kuyper and Wolterstorff give resources for working on justice and renewal of culture.
There’s lots to work with! That doesn’t mean that many or most Reformed churches have used these resources that well in mission, however.
Looks like I have a few books to add to my reading list.