The ELCA is desperately trying to get diverse. Only 1.12% of its members are African-American (but that’s a little better than the .28% of the LCMS). Membership is slowly draining (as is true of most merged mainline churches). Lutheranism remains an ethnic church, made up mainly of Scandinavians and Germans. The ELCA has lots of plans, but they’re still finding themselves frustrated. It’s partly the cultural thing, but the ELCA attempts to connect with cultures (including dishonest outreaches to Hispanics using Our Lady of Guadalupe and calling the service “misa”) just haven’t worked.
I’d be tempted to suggest the liberal Protestantism they were teaching might be the problem, but that wouldn’t be true of the LCMS. More likely, these churches just aren’t used to evangelism. They just don’t like the idea of change. They just aren’t comfortable with unfamiliar faces in the pew next them. As another article to which I linked said, you’re either doing evangelism, or you aren’t.