To paraphrase Churchill’s comments about democracy: Denominations are the worst way to cooperate—except for all the others. They are riddled with weak, ineffective, and arrogant leadership, prone to navel-gazing, and often move more slowly than they should. But these aspects are products of human fallibility and sin. Every time churches work together, ego, failure, and inefficiency will arise. And when they don’t work together, ego, failure, and inefficiency will arise. People, not denominations, are the source.To quote a prof of mine from seminary, "Align yourself with someone and allow them to hold you accountable."
The trouble might be finding a group with whom you can, in a good conscious, align yourself. For instance, I align theologically with one denomination but disagree fundamentally with their methodology. To where then do I go?